The 'protection key' is your USB key plug (dongle). Could it be that you have a damaged USB port or that the keyplug itself is damaged? (A friend stepped on his and the metal connector was loose and only worked if you pushed on it. He has since replaced it.)
ArchiCAD checks for the keyplug during startup and periodically while running.
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB