Audacity only records at the end of recorded sound

Audacity worked very well … but now it only records at the end of track with the longer recording, … I can not append on or modify existing tracks, it does not record on selected track. Shift + record button create (and records on) a new (mono) track, but I can’t record on existing (stereo) tracks… I restarted my PC, and I upgraded from 2.3.x to 2.4… nothing woks!

Thank you for help!

Have you tried setting Audacity to record in stereo?

It works! Thank you for your kind and fast reply! Surely it was my fault, I touched it inadvertently … I searched in all settings, but I did not know what I had to search for.
Again, thank you!