1) upgrade to the latest firmware.
2) Try another PSU
3) Check boards/Fans.
Hope it will help you.
How can I upgrade to latest firmware as I can't even access the machine through IP or LAN.
I have checked with several PSU as I got 22 Antminer s7 from first batch.
Fans and Boards seem to be working fine but can't access the machine as it doesn't connect to the LAN or doesn't assign the IP to access the interface.
Already sent an email to BITMAIN hope to have this solve soon
I would think if you are running that many S7 miners you should invest in some of those long controller cables so you could plug a couple miners into one controller in case one goes down as that is what you may very well have. I believe it was said one controller can run up 9 boards or 3 miners. It would help a lot in trouble shooting a problem.