"Add field group" doesn't appear in Manage form display for Book page node type

Hi adam_b

In my Local Add field group button is visible. I am attaching Screenshot.

Bizarre... it's definitely not there for me. I guess we'll see if anyone else finds this happening. At least I can work around it.

I am experiencing the same issue.

I downloaded and enabled the Field Group module and attempted to use it to modify the form of a custom data type Change Request. At first, I thought it wasn't working at all since the Add Field Group button was not visible in the Manage form display tab of my Change Request data type.

I stumbled across this issue and realized I should check the Page and Article data types that came with my Drupal installation. Surprise surprise, the Add field group button is perfectly visible on there. I'll admit, I wasn't able to find any documentation for this module so I do not know if I am doing something wrong or if this button should be visible on all custom data types within the Manage form display tab.

Anyway, I included the screenshots of page/form-display where it is working, and change_request/form-display where it is missing.

I also wanted to add that the workaround posted in this post works for me as well. If I go to the change_request/form-display/add-group URL I am able to add the group, I just don't see the button.

I just wanted to add an update as I have been working more on this content type today and the button is now mysteriously appearing. I am wondering if this is something to do with caching and it may have been automatically resolved by CRON. I am pretty new to Drupal and I do not know enough about this yet to perform any kind of investigation as to why it didn't work yesterday and why it suddenly works today.

I just wanted to note that I couldn't see the "Add field group" button either until I cleared the cache (`drush cr`)

Confirming -- a supplemental cache clear is needed after installing.