Printer from phone

Hi,

... and do not forget the router. If there is a problem with device discovery (especially, if you have an AirPrint-enabled printer, but also if an iOS app from the printer manufacturer is used), the following power-cycle procedure may help (in this order, with these waiting times): Power off the Wi-Fi router, the printer, the iPhone, and all other devices/computers. Wait two to three minutes. Power on the router. Wait two to three minutes. Power on the printer. Wait a minute or two. Power on the iPhone. Finally, power on all other devices/computers.

More AirPrint information in these articles:

About AirPrint - Apple Support

Use AirPrint to print from your iPhone, iPad, or iPod touch - Apple Support

I would restart or force restart the phone

see here. Restart your iPhone – Apple Support (UK)