Cannot access an app after ios 13.5 update

Were you part of a family sharing earlier?

If you leave the Family Sharing group, you keep purchases paid for using the shared credit card but you immediately lose access to other things the family members share:

• Other family members’ items no longer appear in the Purchased section of the iTunes Store, the App Store and Apple Books.
• DRM-protected music, movies, TV shows, books and apps you previously downloaded are no longer usable if someone else originally purchased them. Other family members can no longer use DRM-protected content downloaded from your collection.
• In-app purchases become unavailable if you bought them using an app someone else originally purchased. You can regain access to the in-app purchases by purchasing the app.
• The family members’ photos album, calendar and reminder list are removed from your devices.
• Family members’ device locations don’t appear when you use the Find My app on iCloud.com or on your Mac, or iOS or iPadOS devices.

For information about leaving Family Sharing using an iOS or iPadOS device, see “Set up Family Sharing” in the user guide for iPhone, iPad or iPod touch.

Are you using two different phone numbers on your XS Max?

If the issue still persists, contact Whatsapp Support team, and ask them.

Regards

Giulio