Salesforce record page blank in the mobile app

Why it happens

Activating a Lightning record page in the App Builder can assign it to both desktop and phone. A page built only from Dynamic Forms field sections, with no standard record detail component, has nothing to show on a phone unless the org setting “Dynamic Forms and Dynamic Highlights Panel on Mobile” is on, and in older orgs it is off.

Confirm it

In the object’s Lightning record pages, check which page is assigned to phones. In metadata, the object’s View action override has two entries, one for the large form factor and one for the small. Pages that still use the record detail component render on phones; pages made only of field sections do not.

Three fixes

1. Reset the phone assignment to the default page. Quickest. Phones get the standard highlights, the details from the page layout, and related lists.
2. Turn on Dynamic Forms on mobile. The field sections render, but phone users get the whole desktop page, every tab and every field.
3. Build a short phone page. The handful of fields people check on a call, assigned to phones only. The best result for the people using it.

Deploy it safely

Deploy only the action override, not the whole object file. Retrieving and redeploying a large object can overwrite changes made since your retrieve. Then test on a phone signed in as a real user, not an admin.