I assume that the blocking of PUA (possibly unwanted applications) is enabled.
Our flashing tool downloads the newest firmware from the internet and then tries to write it to an external device. A virus scanner can classify this as suspicious behavior.
Unfortunately, in this case only temporarily deactivating the antivirus software will allow the flashing tool to start. Or you can wait a few more days until the antivirus software hopefully classifies this file as harmless and does not recognize it as PUA with one of the next signature updates.