It could be a faulty control board, or a bad PSU, nobody here has a crystal ball, you need to provide more details, since you flashed the miner with different firmware it means you have access to the miner's GUI, get us the kernel log ( it could be called syslog or systemlog on your miner), also post a screenshot of your pool/worker details, you can hide any sensitive data if you wish.
first check the internet cables, even a good looking cable may be problematic.
then check if you can see the miner in your network and try to see if there are any readings
PSU is the next as mentioned from an0ther user
next unplug all cables and plug them again
check all system again
