Add-on purchase fails.

I have purchased two add-ons via the Minecraft app.
1. ‘Minecraft Store Item 2 (Minecraft: Play with Friends) (from Mojang)’
2. ‘Minecraft Store Item 4 (Minecraft: Play with Friends) (from Mojang)’
The purchase went through and was paid for.
Afterwards I get the message:
‘Purchase process in progress. It shouldn't take long.’
I waited about 30 minutes.
Further measures:
Minecraft app > Forced stop
Restarted the tablet
Opened the app and went to the add-on.
Message: ‘Last purchase not yet completed’
Action: Click on OK
Message: ‘Purchase process in progress. This shouldn't take long.’
What can I do to get these add-ons to work?