STM32WB55 Nucleo - FUS_STATE_IMG_NOT_FOUND error
I was able to fix it, got a clue from a colleague and this thread https://community.st.com/s/question/0D50X0000Ay9bkd/stm32wb-fus-update-fail-from-101-to-102. Here is what I did:

Deleted the firmware
Loaded stm32wb5x_FUS_fw_1_0_2.bin at 0x080EC000. stm32wb5x_FUS_fw.bin (v1.0.1) didn’t work first time. After I loaded 1.0.2, I was able to load 1.0.1.

After this I was able to flash &quot;stm32wb5x_BLE_HCILayer_fw.bin&quot;.
Apparently the original issue was that the stock firmware had old key and it could not verify if &quot;stm32wb5x_BLE_HCILayer_fw.bin&quot; was valid.