The alarm did not ring (Android)
Allow notifications, "Alarms & reminders" and full-screen notifications for Sidre, and turn off battery optimization for it. Some phones also need Sidre allowed to start in the background.
On the alarm screen, "Try the alarm (1 min)" rings a test, and "Diagnostics" shows what the system has set.
The alarm on iPhone
On iOS 26 and later, allow alarms for Sidre when asked. iPhone keeps the next 16 alarms as system alarms; open the app now and then so the following ones are set too. Before iOS 26 the alarm is a notification sound of at most 30 seconds and is silent in silent mode.
The times differ from my mosque
Check the method in Settings (Sidre suggests the one used in your country), the Hanafi asr and the high-latitude rule. If a difference remains, adjust each time by minutes under Time adjustments.
The qibla looks wrong
Move away from metal and electronics, then calibrate the compass by moving the phone in a figure eight.
Moving to a new phone
On the Tracker screen, tap Export and keep the file. On the new phone, tap Import and choose that file.