Unfortunately, the Time Capsule cannot delete enough information to be able to make room for the new backup.
It would take forever to try to manually delete backups...and might not be successful....so you really are faced with a decison on whether you want to:
1) Add a new Time Capsule and start with a new "master" backup and move forward from there. You can keep the old Time Capsule connected and go back to browse backups there if you need to do so.
2) Erase the Time Capsule and start over with a new "master" backup and move forward from there.
If you really don't need all the old backups from months ago, and you don't mind starting over again, this makes sense for a lot of users. I usually start over about every 6 months or so, but your needs may vary.
The procedure will vary according to the version of AirPort Utility that you have on your computer.
If you are not sure which version that you have, open AirPort Utility, click on the AirPort Utility menu in the upper left corner of the computer screen and click About AirPort Utility fo rthe version that you have.
Post back with that info.
Thanks for the info. To completely erase the Time Capsule drive and start over....
Open AirPort Utility, click on the Time Capsule icon and then click Edit in the box that appears
Click the Disks tab at the top of the next window
Click Erase Disk
Select the Quick Erase option
This will only take a minute or two and then you can start a new backup
I found this solution as I was having the same issue.
I have erased the TC using Airport Utility, and in AU it is now showing as 2TB out of 2TB available.
However, when I open Time Machine preferences it states that the capacity available is still the same as before I erased. Have I missed something?
Thanks for your advice!