Ask Them
The most important question here is why they aren't engaging with you on this. We can't answer that. They can, but you have to ask them. If you do that, be calm and polite. If someone says something that you don't agree with, DO NOT ARGUE WITH THEM! Trying to argue with them about their opinion on this matter will just make them turn defensive, and will either spawn a fight or bad feelings. You have to ask them, and then respect and accept what they tell you even if you don't like it.
Whatever they tell you will give you a starting point on how to address the problem.
Personally - I Hate That Flaw
If I were at your table, I'd consider doing the same thing they are. I have marginalized socially damaging players before. Why did I do that? (Before I answer, I want to point out that it's an entirely legitimate character choice, and everything from this point on is not criticizing you personally or how you want to play.)
Because for myself and other players who love the social interaction part of the game, what you're playing can be toxic if not done carefully. I've seen that type of character cripple social situations by being so rude and stubborn that others (including NPCs) either just say "screw it" and stop interacting, get standoffish, or if they're an authority figure decide to impose their will with force.
For anybody who wants to solve the situation with a lengthy interaction at the table and get what they want with talking, the thing they need more than anything is for a character like yours to not talk. Your character is not helpful to social interactions whatsoever.
Look at it this way - you've created a character that effectively can't help in that aspect of the game. That's alright, but if you engage in that part of the game anyway, you're hindering other players who might enjoy that part of the game and do have characters that can play effectively.
If someone made a character that was so inept at combat that they actively harmed the party every time they tried to fight, how would you feel? Would you start getting annoyed if they keep jumping into combat and making things worse despite being completely and deliberately ill-suited to do so? I'd expect that kind of character to get out of the way and let the combat capable party members handle it.
Just like we don't expect the peasant farmer to take on a dragon and we don't expect the fighter in full plate to lead a stealth operation, we don't expect the socially inept person to screw up our diplomatic attempts.
Also, It's Annoying
Setting that part aside, this can also be annoying just in party interaction. As someone in a party, it's draining to deal with someone else in the party who is stubborn and bull-headed. Those characters can often be "my way or the highway", and that creates party conflict unless everyone just does what your character wants.
I don't know if you're doing that, but I've seen this type of character do it quite frequently, and it's just not fun for me to deal with it all the time.
Do They Want Conflict?
This stands out to me:
instead of engaging with the flaw by trying to address it or even
using it as a conflict driver, simply use it as an excuse to go 'nope,
I'm not going to RP with this character to begin with'.
Have you considered that they might be reacting that way because they don't want to be in conflict like that? Games are supposed to be fun, and if they don't find that situation fun the easiest way to deal with it is to disengage.
Their refusal to deal with it suggests that could be the case, but it's best to ask them.
