Please add the info to check if ttyACM0 is owned by the correct group

[contra-bit]

This Commands shows the incorrect ownership

 ls /dev/ttyACM0 -l  
crw-rw---- 1 root uucp 166, 0 28. Dez 17:54 /dev/ttyACM0

it should be

My System is Arch 5.4.6