Hello Siabh_Saoirse,
Welcome to the community and I'm sorry to hear you're unable to record programs at the moment.
How long has this been happening for? I can see you have rebooted the box but this could be down to a hard drive fault so I would recommend wiping the hard drive and starting again.
You will find this option by going to -
Home - Help and Settings - Clear and Reset TiVo® - and then fourth option down Clear and Delete everything.
The instructions on the screen will then ask you to enter your pin, press thumbs down three times and press the last CH button at the bottom right of your remote.
This should fix the issue you're experiencing with failed recordings but please let me know if there's no change as I would like to book a technician visit for you instead.
Speak to you soon