We recently had Spectrum internet installed. Their wireless router broke our HP OfficeJet Pro 8100 wireless printer in that the spectrum router is dual band and the printer will only connect to a single band wireless. We still a Netgear D2200D modem / wireless router. Can this unit be put into bridge mode and then used to connect our printer? Or is there a better solution, such as getting a new printer?
My guess is no but you have to read the manual. What you need is a CLIENT=BRIDGE.....ie it acts as a end device. This is not common but it might have it.
From the quick look this comes up as a DSL modem and it does not have a ethernet wan port so that likely means it does not have any kind of bridge mode.
It is strange that the printer will not connect. Try to use different SSID for the 2.4g and 5g band.
If that still does not work you can use your old router as a AP. Search for how to use a router as AP, lots of example and youtube videos.
This in effect would be the same as if you could take the wifi chip out of the old router and add it to the new router. Your printer should connect to the radio on the old router and then use ethernet to get to the other router and internet.
Still I would try to make it work with the new router directly. The only thing other than the SSID is the encryption and unless you printer is extremly old it should support WPA.