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?

https://manual.audacityteam.org/man/faq_recording_how_to_s.html#How_can_I_record_in_stereo.3F

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!