I had the same issue. Wyzecam v2 stopped working after i upgraded. I was told to re flash thefirmware. I tried twice and was going to give up.
Finally i noticed that you want to remove the power cable to the wyze cam v2, insert the SD card with the new firmware, KEEP PRESSING THE SETUP BUTTON & Now insert the power cable to wyze cam. This played the trick (the previous time i plugged the power cable first and then was pressing the setup button and it did not work). Within few seconds light turns blue and within a minute it had flashing light and my camera is working fine now.
So, please unplug the wyze cam power connection, load your SD card with new firmware and put it back in Wyzecam v2, now press the setup button and then insert the power cable to Wyzecamv2 and you should be good.