Tell us what you are trying to do?
I'm just trying to create a form when I selected the custom field to add the fields to the form they didn't appear and it caused my site crash because I use the form to upload information from the clients.
This situation is making me loose a lot of time because I can't finish the site and can't show to the client. It seems like there is no communication between custom fields and forms.
Please I need response asap because tomorrow I have a demonstrations of the platform.
The Good news is that I was able to get it to work by creating a new field group and adding some of the fields from the C General field group and it worked on the form. See Screenshot.
So what you will need to do is to create a new field group and re-add the fields from the existing group. You won't need to recreate the custom fields from scratch. You can insert your previously created fields by using the "select previously created fields" button.
The bad news is that your existing C General field group would appear to be corrupted.