Upgrading to Lollipop

[AC Question]

Since upgrading my HTC One M7 to 5.0.2 my phone app refuses to work and will not call the person requested

 

[Rukbat]

Bring the phone in to the carrier.

 

[hallux]

Have you tried doing a factory reset? I suggest making ABSOLUTE sure you have your required info backed up - pics synced to Google, contacts synced to Google, etc. Sometime major OS updates just don't do well unless you start it out "clean" with a factory reset after.

You can also go sub-nuclear and just clear the cache partition - https://www.androidpit.com/how-to-clear-the-cache-on-the-htc-one-m7