Either use the sd card recovery image from Bitmain, or the bos-toolbox, ie. bos-toolbox uninstall ipaddress. Then log into the miner and "update" that firmware to the latest from Bitmain.

Once you have Braiins OS installed just inserting the sd card won't boot from it unless you edit the text file uEnv.txt and add the line sd_boot=yes. I don't think reflashing Braiins OS from sd would make any difference, what you could try is re-enabling the boards (in Miner > Configuration) and lower the powerlimit (autotuning should always be enabled).