Here are the suggested steps to troubleshoot a printer that won’t respond when trying to print from a mobile device using a print app:

1. Power Cycle both the printer and device.
2. Check network connections of both the printer and device.
3. Check that the printer is installed and set as the active/default printer.
4. Check the app to make sure it is compatible with your particular model of printer.
5. Check that all software and firmware are up-to-date.