Hi @Finn_Th3_Boy,
Sorry for the delay in responding to you on this issue. I was wondering if you could go through a few steps to ensure that this person might not have accidentally been added to your Origin block list.
Go to your Origin client, and click Origin at the top. Go to Account and Privacy, then Privacy settings. Scroll down a bit and ensure the person you are trying to add is not on the blocked list.
If this isn't the case, you may need to contact one of our Game Advisors to review your account and see if they can reproduce the issue on their end. You can contact one of our Game Advisors here: https://help.ea.com/en/contact-us/new/