I can't seem to see your screenshots, but from what you described it looks like the situation you'll get before entering the Main title.
In order to fill in the different fields of the Primary details section and then proceed with the other sections, you need first to enter the Main title and confirm that it's not a duplicate. After that, you'll be able to keep going.
So:
1. Enter the title
2. See if the title appears among the "Possible Duplicates" options. If not,
3. Choose "This is not an existing title"
4. Press "Confirm"
https://prnt.sc/EF4LyEPzsnJh
After this, the page should appear like this: https://prnt.sc/AonjbUHlC2_e and you'll be able to add the rest.
** If you already did this, but the page is still not working, then I'm not sure what happened and probably it's a glitch... We'll have to wait for the admins' help ^^''