I think you might have to reinstall the firmware from the web UI and uncheck the save settings tab to go back to factory settings if you can't press the little button on the back. I had the same problem with my one of my S3+ miners and I had to reboot the router it was connected to to get it to start hashing again.
Thanks I figured it out in the end, which was what you just said
My only problem now is the 192.168.1.0 network is assigned elsewhere and if change the configuration of my Cisco router I will loose connection and cut off the rest of miners to the internet!
Looks like I will have to make physical visit anyway now, my own stupid fault
Cheers
