My 2C Pro camera went offline. after none of the suggestions worked I deleted the camera, went through the steps to add it back, and when it advises to “Press the SYNC button for 2 seconds until you hear a Beep” there was no Beep or indeed sign of life even after charging for an hour. The camera was quite hot when i took it down
send feedback to Eufy if they will replace outside warranty period.
otherwise you may have o open it up to change the batteries.