Unable to Airprint: problem appeared recently with no change in equipment

We bought a iMac and Canon 6820a printer last March.  Everything work seamlessly as a wireless network with printer, computer, iPhones, and iPads. In January, 2024, prints began taking up to 45 minutes to start from the iMac and phones could not find the printer at all.  The Geek Squad spent a few hours checking it our and were able to get the iMac printing by assigning a static IP address to the printer.  Phones, however, could not find the printer. The Geek suggested replacing the XB7 router. I exchanged it at the the local Xfinity store and all worked well (including AirPrint) the rest of the day.  The next day, phones could not find the printer.  I can only assume that this "new" router had a firmware update overnight putting back in the problem that had appeared earlier in January. The phones and iMac are connected on 5GHz and the printer is on 2.4GHz but it's all the same network and the router should be able to handle that.  I am not very tech savvy but have read most of the posts on similar problems. How can I get how to get AirPrint working again? Do I need to simply purchase my own router and return this one to Xfinity? (The router no longer shows the separate frequency bands and the iPhones, thus, don't offer a choice of frequency.)