BTT SKR Mini E3 V3.0 - Extruder didn't work ...

[Wollies]

In my Voron V0.2 I'vd install an BTT SKR Mini E3 V3.0 and it worked for more as 500 printing hours. But now - and I don't know why - the Extruder (EM-Port, connected directly to the port) ditn'd work now. I change the Mainboard (I have 2 same Mainboards), change the extruder for an sherpa micro, checked the cabels - I didn't find a problem! The extruder won't work in this configuration!

Did you have an idea, whats the problem could be ... ?