Time capsule can't back up automatically after first sucessful back on catalina ERROR 45

When you say reset.. do you mean restart??

I recommend you do a factory reset of the TC. No files on the hard disk are lost.

Hold in reset button without power.. then apply power to the TC without releasing reset for at least 10sec.. front LED will flash rapidly if successful. Wait for the TC to fully reboot..

Open the Airport Utility from Catalina and give the TC a short name.. less than 8 characters, No spaces and pure alphanumerics. Also password same rules but 8-20 characters.

You will need to change the setting in Time Machine to point to renamed TC. It will state it is going to start a new backup but will start (after 120sec) and discover the existing backup, spend some time checking and then .. hopefully .. continue with the next incremental.

NOTE.. yes.. Time Machine on Catalina is unreliable. Particularly to network target like Time Capsule.

Strongly recommend investing in a decent backup software like Carbon Copy Cloner.

Did you upgrade from the previous OS? And Time Machine has backed up over the existing backup or created a new backup?

Check if you have two backups.. both with same computer name but one will be sparsebundle and the other backupbundle.

I know you stated the network is working perfectly but Time Machine can be very picky.

Can you open Time Capsule disk in Finder and copy files to it and read them back to the computer?

Try doing that just before you start the backup.

Is the TC the main router for the network? If not there are a number of issues that can arise with bonjour being unable to find the TC. The error 45 is much like error 1 and is an old problem.

See https://www.baligu.com/pondini/TM/C17.html

From previous posts people used the methods pondini suggested there to fix error 45.. but Catalina might be more difficult.

Notice that the TC name appears to be BING.local

Does this domain agree with the main router? If not the computer may have issues finding it.

Open a Terminal and just type ping BING or whatever your TC name is.. and then try ping BING.local

Make sure in the computer network preferences that the search domain is blank or set to local.

There is another way around the problem.

Instead of using the TC use its IP address.

So try the following. NOTE.. this is not from Catalina as I simply don't trust it.

Setup the TC as a share in Finder using its IP.

Step 1 Open Airport Utility and click the TC icon to get summary page and the IP address.

Your setup will be different but you can see my IP on the TC is 192.168.20.10

Step 2 In Finder create a link to the share. There are various methods to do it.

Click connect and type in the user and password.

I forgot to remember.. but do check the password to save in keychain.

It should open the share in Finder.

Now go to the Time Machine Preferences add disks.

The TC hard disk share data is now listed both by IP and name of the TC.. pick the IP

I was not asked if I wanted to replace so it simply swapped from the data on tc5e to data on 192.168.20.10

And says it will do the first backup but will actually find the old backup and start next incremental.

If all of that does not work.. Then you really need to start over.

Delete the backup and restart it.. I suggest you do this properly by erasing the TC disk.

If you really want to pursue getting Time Machine to work, since you have changed the name of the TC and reconfigured it with all short names.. all that is left is to archive off the existing backups, erase the TC disk and start over. That is still no guarantee it will work properly into the future.

To just get a backup that does work.

The alternatives are to get a USB drive and plug it into the computer, format it APFS I think is now required with Catalina and use that for your Time Machine target. Or get an alternative backup software.