Why won't my Apple devices print using the new T-Mobile Cylinder/ Gateway router's wifi?

I used the search function and found this solution.

If the solutions from the thread link above (from 007BondMI6) didn’t solve your problem, would you please supply more info about your setup? This might help the community better help you with this problem.

For example, are all devices (including printer) connecting directly to the gateway’s wifi network, with no other wireless routers, switches, etc., being used? If other routers, switches, etc., are being used, to which network devices are each of the apple devices and printer connected? What printer are you using?

I’m connecting my printers and devices (including two iPads, an iPhone XR, a MacBook Air, a variety of Windows and Android devices, and three different Epson printers) to a Netgear Orbi router (router is in AP mode). The Orbi is connected to the T-Mobile Nokia gateway via ethernet cable. All my devices print to any printer without any problems.

I did try printing one time from an iPad that was connected directly to the T-Mobile gateway wireless network, forgetting that it needed to be on the same network as the printer, I got the “no air printers found” error message. When I connected my iPad to the Orbi router network, printing worked.

I also had a similar “no air printers found” problem on a different broadband system (not T-Mobile). In that case, the solution was to reset the printer, which disconnected it from the wifi network. Then I setup up the wireless connection again on the printer, and I could print to it. If all else fails, you might try that.

Had this problem and after much research I developed a very simple solution.  The Nokia T-Mobile modem is not compatible with AirPrint.  As I already had an Archer router with its own WiFi network name, I used the T-Mobile app to create a separate WiFi network for the T-Mobile Internet modem.  I connected the router to the modem via ethernet and kept my Archer network unchanged.  The new T-Mobile network is idle, but the Archer network works just like it used to, including compatibility with AirPrint printers!!!  

And an added benefit, the ethernet wired Archer A20 WiFi network is 2 to 4 times faster than the T-Mobile network!!  

Likely good advice for someone who knows what they’re doing.  But I know little but did set my HP OfficeJet 4630 to iPv6 only.  After doing so the printer could not be found and attempts to connect to it via WiFi failed.  Fortunately I still had the old USB cable and connected and reset to iPv4 or iPv6.  

That said I’ll still keep my own Archer network and keep my two networks for dummies solution.  

Yes, we had to change our Cannon printer to use WPA2 security as well before I would connect to Wi-Fi. I assume, it being an older printer would necessitate this.