Some sort of error message should appear.. if not open the console and do a search for backup.
The actual error message helps loads to understand the issue.
I have run disk disk utility first aid on the time capsule, but still no backups appear in time machine.
Disk utility is useless for checking the Time Capsule.. it is a Network drive.. disk utility is only for local drive.. although you can also check the time machine backup when it is mounted on the computer since it is a special file called a sparse bundle.
13.6GB available of 998Gb
Your Time Capsule is very old.. and very full.
1TB version were sold up to 2011.. that makes it 9-11 years old.. it is well past replacement.
13.6GB is actually minimal space left. Time Machine is very inefficient in the way it uses disk space.. so to copy a 100MBytes it might need 2GB of space. Also Time Machine has lost the ability to delete sufficient files to continue backing up.. you need to make a decision.
1 Replace the TC. e.g. use a USB drive plugged into the laptop.. this is the fastest, cheapest and most reliable solution.
2 Erase the TC and start over.
3 Archive the TC to a 1TB hard disk and then erase and start over.
but time machine software has somehow got confused
Very common problem with new OS every 12-18months and massive patches in between.
If you just want to see if the current backups are ok.. hold down the option key and click the Time Machine icon in the top right menu area.. choose verify backups.
Your Time Machine seems to be finding the backup since it is showing you the dates just fine.. it simply cannot continue to backup. Size limitation? Corruption??