No protocol error when using einstein sentiment JWT

Question

I am getting an error when I try to implement einstein sentiment, this is the error: 'no protocol: IU3....OIE"'

The code stops running after I do a http.send. I am not sure what is going wrong, anyone an idea?

This is my code:

public class JWT {

    public String alg {get;set;}
    public String iss {get;set;}
    public String sub {get;set;}
    public String aud {get;set;}
    public String exp {get;set;}
    public String iat {get;set;}
    public Map<String,String> claims {get;set;}
    public Integer validFor {get;set;}
    public String cert {get;set;}
    public String pkcs8 {get;set;}
    public String privateKey {get;set;}


    public static final String HS256 = 'HS256';
    public static final String RS256 = 'RS256';
    public static final String NONE = 'none';


    public JWT(String alg) {
        this.alg = alg;
        this.validFor = 300;
    }


    public String issue() {

        String jwt = '';

        JSONGenerator header = JSON.createGenerator(false);
        header.writeStartObject();
        header.writeStringField('alg', this.alg);
        header.writeEndObject();
        String encodedHeader = base64URLencode(Blob.valueOf(header.getAsString()));

        JSONGenerator body = JSON.createGenerator(false);
        body.writeStartObject();
        body.writeStringField('iss', this.iss);
        body.writeStringField('sub', this.sub);
        body.writeStringField('aud', this.aud);
        Long rightNow = (dateTime.now().getTime()/1000)+1;
        body.writeNumberField('iat', rightNow);
        body.writeNumberField('exp', (rightNow + validFor));
        if (claims != null) {
            for (String claim : claims.keySet()) {
                body.writeStringField(claim, claims.get(claim));
            }
        }
        body.writeEndObject();

        jwt = encodedHeader + '.' + base64URLencode(Blob.valueOf(body.getAsString()));

        if ( this.alg == HS256 ) {
            Blob key = EncodingUtil.base64Decode(privateKey);
            Blob signature = Crypto.generateMac('hmacSHA256',Blob.valueof(jwt),key);
            jwt += '.' + base64URLencode(signature);  
        } else if ( this.alg == RS256 ) {
            Blob signature = null;

            if (cert != null ) {
                signature = Crypto.signWithCertificate('rsa-sha256', Blob.valueOf(jwt), cert);
            } else {
                Blob privateKey = EncodingUtil.base64Decode(pkcs8);
                signature = Crypto.sign('rsa-sha256', Blob.valueOf(jwt), privateKey);
            }
            jwt += '.' + base64URLencode(signature);  
        } else if ( this.alg == NONE ) {
            jwt += '.';
        }

        return jwt;

    }


    public String base64URLencode(Blob input){ 
        String output = encodingUtil.base64Encode(input);
        output = output.replace('+', '-');
        output = output.replace('/', '_');
        while ( output.endsWith('=')){
            output = output.subString(0,output.length()-1);
        }
        return output;
    }

public class JWTBearerFlow {

public static String getAccessToken(String tokenEndpoint, JWT jwt) {

    String access_token = null;
    String body = 'grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer&assertion=' + jwt.issue();

    HttpRequest req = new HttpRequest();                            
    req.setMethod('POST');
    req.setEndpoint(tokenEndpoint);
    req.setHeader('Content-type', 'application/x-www-form-urlencoded');

    req.setBody(body);

    Http http = new Http();    

    // Code runs untill here, then error occurs
    HTTPResponse res = http.send(req);

    if ( res.getStatusCode() == 200 ) {
        System.JSONParser parser = System.JSON.createParser(res.getBody());
        while (parser.nextToken() != null) {
            if ((parser.getCurrentToken() == JSONToken.FIELD_NAME) && (parser.getText() == 'access_token')) {
                parser.nextToken();
                access_token = parser.getText();
                break;
            }
        }
    }
    return access_token;

}

}

public class CustomSentimentAnalysis {

@AuraEnabled 
public static List<Probabilities> getCaseAnalysis(String sentimentModel , String textToAnylize){

    ContentVersion base64Content = [SELECT  Title, VersionData FROM    ContentVersion WHERE   Title = 'einstein_platform' LIMIT 1 ];
    Einstein_Settings__mdt einsteinSettings = [Select DeveloperName, Label , Account_Email__c , Service_EndPoint__c , Token_EndPoint__c 
                                               from Einstein_Settings__mdt where DeveloperName ='Sentiment' Limit 1]  ;   
    DateTime tokenExpireTime = DateTime.now().addMinutes(30);
    String tokenExpireTimeinUnixFormate = ''+tokenExpireTime.getTime()/1000;

    String keyContents = base64Content.VersionData.tostring();
    keyContents = keyContents.replace('-----BEGIN RSA PRIVATE KEY-----', '');
    keyContents = keyContents.replace('-----END RSA PRIVATE KEY-----', '');
    keyContents = keyContents.replace('\n', '');

    JWT jwt = new JWT('RS256');
    jwt.pkcs8 = keyContents; 
    jwt.iss = 'developer.force.com';
    jwt.sub = einsteinSettings.Account_Email__c ;
    jwt.aud = einsteinSettings.Token_EndPoint__c;
    jwt.exp = tokenExpireTimeinUnixFormate;

    String access_token = JWTBearerFlow.getAccessToken(einsteinSettings.Token_EndPoint__c, jwt);

    Http http = new Http();        
    HttpRequest req = new HttpRequest();
    req.setMethod('POST');
    req.setEndpoint(einsteinSettings.Service_EndPoint__c);
    req.setHeader('Authorization', 'Bearer ' + access_token);
    req.setHeader('Content-type', 'application/json');        
    String body = '{\"modelId\":\"'+ sentimentModel + '\",\"document\":\"' + textToAnylize + '\"}';
    req.setBody(body);    

    HTTPResponse res = http.send(req);  

    JSONParser  parser = JSON.createParser(res.getBody()) ;
    String label ='';
    Decimal probability = 0 ;
    List<Probabilities> probabilities = new  List<Probabilities>() ;
    while (parser.nextToken() != JSONToken.END_OBJECT) {
        if (parser.getCurrentToken() == JSONToken.FIELD_NAME) {
            String text = parser.getText();
            if (parser.nextToken() != JSONToken.VALUE_NULL) {
                if (text == 'probabilities') {
                    probabilities = new List<Probabilities>();
                    while (parser.nextToken() != JSONToken.END_ARRAY) {
                        probabilities.add(new Probabilities(parser));
                    }
                }   
            }
        }
    }
    return probabilities ;


}

public  class Probabilities {
    @AuraEnabled
    public String label { get; set; } 
    @AuraEnabled
    public Double probability { get; set; }
    public Probabilities(JSONParser parser) {
        while (parser.nextToken() != JSONToken.END_OBJECT) {
            if (parser.getCurrentToken() == JSONToken.FIELD_NAME) {
                String text = parser.getText();
                if (parser.nextToken() != JSONToken.VALUE_NULL) {
                    if (text == 'label') {
                        label = parser.getText();
                    } else if (text == 'probability') {
                        probability = parser.getDoubleValue();
                    }  
                }
            }
        }
    }
}

}