Is your app public, public with email, or whitelist? If it’s public it won’t track logins in the App:Login sheet. Also that sheet will only show a login per user, per device at the moment they request a new pin. Once they are logged in on a device, it is not tracked.
I’m not entirely sure how the stats work on glideapps.com, but I believe it’s similar. I feel like it’s unique users/devices within a 30 day period. If they are already logged in on the device, then the stat doesn’t update.