xTimerIsTimerActive() returns pdFalse, though timer is running and CB is executed.
Any idea why is that?

xTimerGetPeriod() doesn’t work as well.
xTimerGetExpiryTime() doesn’t work as well.

pcTimerGetName() does work, though.

Thanks for help,

Sounds weird. My first guess: Wrong timer handle or an other programming issue.
You should add the FreeRTOS version and platform/MCU you’re using and if possible the related code. Otherwise it’s hard to know…