Hello SalehAbullah,
That's a great question! The alarm should go off at the set time no matter the orientation of the iPhone. If you've verified the alarm was still set, the next step would be to restart the iPhone. While restarting is a simple step, it can help with resolving many issues.
- "Press and hold either volume button and the side button until the power-off slider appears.
- Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
- To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo."
Restart your iPhone
If you continue to have issues after restarting your iPhone, you'll want to make sure you're running the latest iOS version. iOS updates can provide fixes and security improvements that may help with resolving this issue. If you need to reference the steps for updating, they can be found in the following article.
Update your iPhone or iPad
Take care!