Hello.

I don´t see Design tab on your screenshot, even that this post is under Portal engine section. Do you use ASPX templates, or do you have some user personalization set, so your current user can´t see Design tab? Could you please try it as global admin?

Also, do you have some record in your Event log, when try to check-in document on Page tab? It works on my instance with the latest hotfix applied. Could you please try to apply the latest hotfix to see, if it helps? Thank you.

Best Regards,
Radek Macalik