Can't Connect to 2.4 Ghz on Home Network

Keep getting a message that I can't connect to my 2.4 GHz network but I am able to connect to the 5 Ghz network. I have Verizon FiOS and I am using their Quantum Gateway Router. Verizon configures the router to separate the 2.4 and 5 GHz networks with different names. Within the last few days I noticed that I can't connect to the 2.4 GHz network. I restarted the router a few times. I applied the 10.11.6 update so I am thinking it might be related to that. Why go to the slower network? My printers are connected to the 2.4 GHz network and for some reason when I switch to the 5 GHz network the printers go offline (this only happened when Verizon pushed out the firmware update to separate the networks). So to print I need to switch networks. Also noticed that access to a few hardware devices only connect when I am on the same network as them. Many issues here but hoping someone can help with at least getting my mac back on the 2.4 GHz network. Thanks in advance.

Tom