I guess I have the same problem as most people have had with the door to door salesman that sold me a 5G router. The rounter never worked with my printer. My printer is less than 2 years old but will only work with 2.5G rounters. I was acutally using my own router with Xfinity that had 2 speeds (inckuding 5G) I unplugged it the same day and put it in a box. It took me almost a month to return it after many attempts. Finally I got a retun Authoirizaton and off it went. Well now I am getting monthly bills for $75 and owe $140. Cannot get a live person to talk with me as they say I must bring my account currrent before they will talk. Thank goodness that I do not have my cell phone with these people. I have no idea of how I am going to fix this before they try t trash my credit.
I am only able to address your technical problems. First, I think you meant 2.4GHz and 5GHz as frequency bands. 2.4GHz is used by 802.11n standard, which is the wireless standard used by the majority of wireless printers and other IoTs. 5GHz is used by newer WiFi standards such as WiFi 5 and 6. The problem why the router wasn't able to connect the printer is that it may have the SON on, so the printer, a 2.4GHz client, is being incorrectly steered to 5GHz band. The solution is either to turn off the router's SON, so that the 2.4GHz and 5GHz bands become two separate bands, or enable the IoT wireless SSID, dedicated for the IoTs.