Tvheadend

Not a lot anyone can say with that little information.

Can you switch on debugging in the webUI, please (bottom right, arrows, cog) and try to make a recording - see what messages appear.

You also don't say if you're trying to record from the web page or from something like Kodi, and that's relevant because of access permissions.

So, in no particular order, check these initially:

1. That your recording path is set and valid
2. That user hts can create, list and read files in that path
3. That whatever user you're logging in as has access to the dvr functions (access control rules)

You might also want to try to record what you're watching, as that rules out any tuner issues.