I noticed five “Tiles Missing” things in the Android mobile app today. Aeon HEM devices, Minimote, and Plantlink DTHs all broken. Searching this forum reveals this is not uncommon and triggered by ST platform updates.
When I get time I’ll try to update the custom DTHs and delete and re-add the things.
Since you said you are new, heads up, stuff breaks like this on SmartThings quite frequently. I have to fix one thing or another almost every week.