My LaserJet 1536dnf multifunction printer/copier/scanner (MFP) worked great for the first few months we had it, but has stopped working for no apparent reason. It no longer communicates with any of my computers, regardless of which USB port it's plugged into. In macOS 10.12, the print queue shows the printer as offline and not connected, even though it's turned on and plugged into my computer's USB port. It also won't copy or scan anymore. For a while, the display on the MFP was showing what appeared to be error symbols, one of which was a triangular arrangement of circles, but I haven't been able to identify what the code meant and now the display is staying dark. We've even replaced the toner cartridge, to no avail. Have any of you encountered these problems and been able to work through them?