The B550 Bazooka supports the 3600 by default, so it should've at least started with it. Then you could've updated the BIOS using M-FLASH from the BIOS, which is always the best option if your CPU is already supported by the previous BIOS. How did you flash the BIOS, did you use the Flash BIOS Button? Then maybe it didn't work correctly, so you might have to try to flash it again until it works.
First you can try a Clear CMOS by bridging two pins with a screwdriver (the manual explains where the pins are).
Then try flashing again with different USB sticks. Do it exactly by the instructions.