Problems posting in IG and linking the posts w/ FB

Good afternoon,

I am experiencing some problems with my posts on IG. The option to link them to FB and post at the same time is not working.

I am managing multiple business accounts, I have all FB pages connected to the IG accounts (through my personal account), and I even tried the new FB feature Account Center to try to link the posting at the same time (and with the Account Center it works, but just with one account). Overall I am not getting any results.

Everytime I post on IG, when I click on FB to link the post, it is redirecting me to a FB login, and then a code generator.

Do you know how can I fix that problem without login in in each post I want to publish and link to facebook?

Thank you in advance for all the help.