I can't find the "add a repeatable field" button in the BackOffice of a new "Custom field".
I've done this dozens of times and now I can't find the button, even though it usually worked.
I usually add a multitude of repeatable custom fields in the page.php template and even in custom templates (like the home page > page-template/home.php).
Here in the BackOffice, when I create a new custom field, usually after the first record, I had the second "add a repeatable field" button disappearing, but this is no longer the case for this site.
Usually the button to add a repeatable field group is greyed-out until the field group display settings are set to a single post type, which then unlocks the button.
In your case the button is not being displayed at all, which is odd.
I can see you also added additional display conditions to this field group. If you remove them and save the group, does the button re-appear?
If you create a new field group and assign it to some post type (any), does the button appear on that new field group?
I checked the relationship screen at WP Admin -> Toolset -> Relationships and saw a notice about the pending update for the relationship structure.
( screenshot: hidden link )
The repeatable field groups are also stored in the same structure as the post-relationships. This is why their option is not available now. I'll recommend completing the relationship structure migration. After that, you can add the repeatable field groups too.