How to add private pod as dependency?

Question

Below is my podspec

>     Pod::Spec.new do |spec|
>     
>       spec.name         = "SDK2"
>       spec.version      = "1.0.1"
>       spec.summary      = "XXXXXXXXXXXXXXXX"
>     
>     
>       spec.description  = <<-DESC
>               XXXXXX
>                        DESC
>     
>       spec.homepage     = "https://bitbucket.org/dev/SDK2/src/Master/"
>       spec.license      = "MIT"
>       spec.author       = { "xxxxxxxxx" => "name@gmail.com" }
>       spec.license      = { :type => 'No License', :text => 'Copyright (c) 2021 XXXXXXX' }
>       spec.platform     = :ios
>       spec.ios.deployment_target = "13.0"
>       spec.source       = { 
>                           :git => "https://user@bitbucket.org/dev/SDK2.git", :tag
> => "#{spec.version}",
>                           :git => "https://user@bitbucket.org/dev/PrivateSDK.git", tag: =>
> "#{spec.version}" 
>                         }
>       spec.source_files  = "SDK2/**/*.{swift,h,m}"
>       spec.public_header_files = "SDK2/**/*.h"
>       spec.dependency "FBSDKLoginKit"
>       spec.dependency "FirebaseCore", "~>5.0.2"
>       spec.dependency "Masonry", "~>1.0"
>       spec.dependency "SnapKit", "~>5.0"
>       spec.dependency "MarqueeLabel", "~>3.2"
>       spec.dependency "PrivateSDK", "~>1.0.1"
>     
>     end

here PrivateSDK is my private pod. I am unable to add this, it's throughing below error

-> SDK2 (1.0.1) - ERROR | [iOS] unknown: Encountered an unknown error (Unable to find a specification for PrivateSDK depended upon by SDK2.

I tried following solutions, but didn't work anything.

spec.dependency "PrivateSDK"

pod lib lint --sources=XXXXXXXXXXXXX(Private SDK bit bucket link)