Cannot network print to 2350DN

My 2350DN had been working fine, but recently I am no longer able to network print.  When I look at the print queue, the item is sitting in the queue as "printing", but just sits there with a few kb of the job done - even overnight, it gets no further.

I can print fine using USB, and I can access the printer's web page which suggests that the network is running fine.  I have the same problem across three different computers (Win10 and SBS2011).

I have tried:

- Printer reboot

- Firmware update (I was already running the latest firmware)

- Reinstall drivers

Any suggestions as to what to do next?

Thanks

Richard