(PSN)Hobwhal

Hi, long time fan here. Recently been trying to get back into it with the cross-platform play and being on xbox instead of psn nowadays. My Xbox account doesn't have the same login credentials as my psn account. Why can't I manually enter my credentials to connect the correct account? This is incredibly infuriating as I have a lot of good frames and primes on my psn account and has caused me a lot of stress trying to navigate.