my iphone 7 plus is not ringing for incoming calls

Did you check is your iPhone get muted ?

You can change it by switching the mute toggle on the left hand side of your iPhone.

If your iPhone is not muted, check if your phone volume is turned up ?

Also, check the Sounds and Haptics Settings.

If it is still not working, you may reset your iPhone settings by going into --

Settings > General > Reset > Reset All Settings

Warning ! This won't wipe your iPhone, but it will wipe your WiFi, bluetooth, etc. Except Apple ID & some password settings (Passcode & Restrictions, for example)