You might be a bit shocked to see that your ACF field groups are missing in the backend editor after a plugin update. But your WordPress website still works and you do see the contents that was entered in those custom fields on every page you used that plugin for.
It will then look like this where all your fields seems to have been deleted, they won’t even show up in the backend editor of your pages:
The solution to restore those fields is simple. You might have just only missed a simple step after updating your ACF plugin, which is to update the website’s database.
There’s two ways to do that:
1.) The first way is to go to Dashboard on the top left part and look for “Upgrade Database”. Just click that and you website’s database will be updated.
2.) The second way is to go to “Custom Fields” and on the top of the empty Group Fields list will be a reminder by the ACF plugin for you to update the database. Just click the “Upgrade Database” button and that should fix the missing fields.