[Resolved] Custom Fields don't show up on new Post Types

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[jimG-6]

I am trying to add custom fields to a custom post type, but the Field group doesn't want to apply to the assigned CPT.

I created a new CPT
I created a new Post Field Group
I created Fields in the Field Group.
Inside the Field Group I've assigned the Field Group to appear on the new Post Type. Saved the settings.
In the post types overview, on the row of my new Post Type, the Field Groups column shows that the Field Groups are assigned.
I edit the new Post Type, and the section "Post Fields to be shown as columns in Post Type Listing in WordPress Admin" displays:
"Post Fields to be shown as columns in Post Type listing in WordPress Admin
You can include some Post Fields in the listing page for test cpts. Add Field Group(s) to this Post Type and you will be able to select which fields will be displayed in the listing page."
Issue: The Field Group does not appear in the Post Type settings. And non of my fields show up there when creating a post in the Post Type.

I've cleared both WordPress and server varnish cache.
I've cleared custom fields cache in the Front end content settings.
I've attempted to delete the Post Type and the Field Groups with it's fields and start over new.

Nothing solves the issue; I cannot use Custom Fields on newly created Post Types (classic editor). I can still create new fields for existing post types and field groups.

PS: I'm doing this on the staging version of my live site. The live site has the Toolset subscription. The staging always deploys to the live.

[Minesh]

Hello. Thank you for contacting the Toolset support.

I just try to follow the steps you followed and created new Custom Post Type "Book" and custom field group and assign this custom field group to display with "Book" post type and added a single line field "book-name" to this custom field group.

When I edit the post type "Book" I can see the custom field is available under section "Post Fields to be shown as columns in Post Type listing in WordPress Admin". Please check the following screenshot:
- hidden link

I see you are using number of third-party plugins. In order to minimize the cause of the issue and to ensure there is no conflict between the plugins/theme you are using:

Could you please try to resolve your issue by deactivating all third-party plugins as well as the default theme to check for any possible conflicts with any of the plugins or themes?
- Do you see any difference?