Cannot print on printers connected to 2.4G WiFi from computers on 5G WiFi.

Why is it with the Nighthawk M2 Router (MR2100) that devices connected to 5G WiFi or via network cable to the RJ45 port, either stand-alone of through a switch, cannot print to printers connected to 2.4G WiFi? I've had to connect all of my devices to 2.4G WiFi in order to give them print access.

Applies to all computers on 5G WiFi ;- running Windows 7(two computers 32 and 64 bit),8.1(64 bit),10(64 bit)

Printers ;- Brother MFC-J825DW, HP Photosmart eStn C510a

MR2100 firmware NTGX24_10.17.10.00