This happens when the app cache gets corrupted or your phone runs an outdated OS version. Go to your phone settings, find the McDonald's app, and clear cache (not data, unless you're logged out anyway). If that doesn't help, uninstall completely and download fresh from the store. Make sure your iOS is 13+ or Android 8+, older versions aren't supported anymore.
Password managers sometimes autofill outdated credentials. Type your email manually to avoid hidden spaces or wrong characters. Use the password reset option if you're unsure. After three failed attempts, the system locks you out for 15 minutes as a security measure. If you're switching phones, log out from the old device first, simultaneous sessions sometimes conflict.
The GPS permission might be set to 'while using' instead of 'always'. Go to phone settings and grant full location access. If you're indoors with weak GPS signal, manually select your restaurant from the list. Background location refresh needs to be enabled too, otherwise the app uses your last known position from hours ago.
Notification settings have two layers: phone system and in-app preferences. Check both are enabled. On iPhone, go to Settings > Notifications > McDonald's and allow all types. Android users should disable battery optimization for the app under Settings > Apps > Special Access. Notifications get blocked when the app sits unused for weeks, open it at least once monthly to keep them active.