What OS on your PC’s ?
.
What could go wrong
[Solved] Windows does not see my phone in Fastboot mode because needed drivers are not correctly installed
Tip :
if not properly "installed in your path” as explained in Installing adb and fastboot on Windows PC or in Installing adb and fastboot on Linux PC,
simply add ./ at the beginning of all your adb or fastboot commands,
it will use the version included into the relative folder (the latest) instead of the one installed on your system (that can be outdated)
.