ACF loads the JSON file first everywhere but when editing a field group. When editing a field group ACF pulls from the database only. In order to sync the field group you need to go into the list of field groups and sync them manually.
Depending on what you’re looking to do it might be possible to force the syncing, look at the field group and the date is was modified and then call the ACF function to import the group, which is the function that does the synchronization. I can’t give you specifics, because I don’t know them.
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