Suddenly only mono sound on mic

Hi there, after the first problems I finally seriously could work on a song in Cubase 11 artist. So my inspiration grow and I started an other project. But now suddenly my mic. Appears only in mono in my track. I see two lines but only one of them records. While iny other

1 microphone, it must be mono!

Make sure you are using a mono input bus, not 1/2 of a stereo one.