The “not loading” issue has been there for a while now. One way to fix it has been to “kill” to ST mobile app and restart it. ST is slowly doing away with the Classic SHM (for example once uninstalled it cannot be reintalled). It’s best to report it to ST support so they can tag issues together and prioritize them.
You may want to look into the new app STHM (but it has no direct control from SmartApps unfortunately) or check out alternative apps for security like: [RELEASE] Security System: Intruder Alert with Actions