After OSUpdate device not booting from slot B even after marking

I was able to fix this with fastboot --set-active=a followed immediately by fastboot flash boot and all the other partitions

I had to install Android 9 on both (You can check the active slot with fastboot getvar current-slot , and select a slot with fastboot --set

fastboot_ error_ failed to identify current slot This command provides information about the active slot from which the device is currently booting user $ fastboot getvar current-slot Dump

fastboot set active slot  set_active SLOT Set the active slot n oem Execute OEM if (fb->GetVar != fastboot::SUCCESS