If Mylio Photos reports something wrong with a Catalog for a computer, attached drive, or a phone/tablet, the Repair a Catalog tool can be initiated from the Help menu > Show Support Options on Startup.
Click the ellipsis icon in the top app bar (3 dots in the upper right corner).
Select Help, then choose Show Support Options on Startup.
Quit and re-open Mylio Photos.
From the Support Options dialog, choose Repair a Catalog.
Select Main Catalog if the computer catalog says it needs repair. Select an attached USB drive if Mylio reported the external device needed repair.
Skip the corruption check.
Open Mylio Photos on another device signed into your Mylio account, like a computer or phone/tablet. Mylio Photos will sync from the other device and repair the catalog.
If the Mylio Photos application will not launch, or crashes shortly after opening, ensure all Mylio processes are quit, then hold down the alt/option key while launching the Mylio Photos application to show Support Options.
On a phone/tablet, you can access the Support Options by pressing and holding the Mylio Photos app icon from the Home screen to reveal a Context Menu. Select Support Options..