Time Machine backups 24 hours, no further

I would first check to see that you have the frequency of TM backups set the way you want. From menu bar, click on options and check frequency.

See what happens if you safe boot the mac and see if there are more backups, assuming you set the frequency for e.g. every hour

If the frequency is right (e.g. every hour), I would start up the mac and repair the TM drive by starting up with command-R and selecting disc utility and repair the TM drive.

If all else fails, I would erase the drive and start over, assuming you have a backup of your data some other way or on a different drive.