Hi peace279,
You started from a good resource: Use AirPrint to print from your iPhone or iPad - Apple Support
For help with printing be sure the printer is connected to your network with the help of the steps here: Connect an AirPrint printer to a Wi-Fi network and check for any printer driver updates from your manufacturers website.
If the issue continues, confirm your model is listed here: About AirPrint. Next, restart the printer and your iPhone to test. You can also confirm and check your Wi-Fi settings with the help of the article here: Connect to Wi-Fi on your iPhone, iPad, or iPod touch - Apple Support
Should the issue remain after completing the steps and checking your settings, reach out to Apple Support directly to further assist. Get Support
Best.