Re: Zoom modem 5341J DOCSIS 3.0
Usually if the Upstream is flashing and not solid it means there is a problem with the upstream (return) path of the modem.
Log into the modem by typing 192.168.100.1 in the address bar of your browser.
Check to see if there is a status page and note the upstream/downstream power levels.
Most likely not an issue with the modem but either faulty wiring or problem on the ISP side.