Runtime error COUNTDOWN

my app was working correctly with the "countdown_timer method
cancel “, suddenly started giving the following error:” Runtime error - void android.os.countdowntimer.cancel () 'on a null object reference "
Somebody help me, please.

Are you using extension for this.

It would really help if you provided a screenshot of your relevant blocks, so we can see what you are trying to do, and where the problem may be.

To get an image of your blocks, right click in the Blocks Editor and select “Download Blocks as Image”. You might want to use an image editor to crop etc. if required. Then post it here in the community.