Delete previous email (owner) for which I no longer have access to keep my other email (co-owner) as the single owner

I transferred my Box from Company A to Company B by making my email from Company B a co-owner. However, I forgot to delete my email from Company A. As of today I no longer have access to Company A Box, and I am getting errors in sharing links because they request the password of Company A. I believe that deleting my email from Company A (the owner) and making my email from company B (co-owner) the single owner would solve that. However, I cannot make that change because the option is greyed out. What should I do?