Try click on the Time Machine "clock" icon at the top of your Macs screen
Click on Open Time Machine Preferences
Click on Add or Remove Disk
Click on the Time Capsule Disk.....named "Data" unless you have renamed it....to highlight it
Click Remove Disk
Restart your Mac
Open Time Machine Preferences again and click on Select Disk or Add or Remove Disk
Select the Time Capsule
Click Use for Backup
See if backups will begin again.
Time Machine will usually act like it is going to make a whole new complete backup of your Mac, but after a time (this might be an hour or two depending on how much data that you have on the Time Capsule), Time Machine will usually recognize that you have old backups and add to them.
You won't know if this is successful until the backup is completed. Even when the backup is completed, it may take a few hours for Time Machine to completely index everything and display backups correctly.