Sierra Time Machine / Time Capsule problem
After installing Sierra, I'm unable to use Time Machine to a Time Capsule.
There was a MacBook Air with two bootable partitions. The Macintosh HD partition had a Yosemite system and the "Second" partition had an El Capitan partition that was created by a clean install and then allowing Migration Assistant to copy over from Macintosh HD all accounts, settings, networks, and other files. Both partitions were being backed up by Time Machine to a Time Capsule. The Macintosh HD partition was erased and Sierra was installed on Macintosh HD and Migration Assistant was allowed to copy over from Second all accounts, settings, networks, and other files.
Time machine has not been working since. It gets the error message "Backup Disk Not Available." However, using the Finder, I can mount the Time Capsule, open the sparsebundle and see all the individual backups. Since I had erased Macintosh HD, I went through the steps at http://pondini.org/TM/B6.html to "reconnect to my backups". That didn't make any difference (probably because Time Machine isn't really seeing the the sparsebundle on the Time Capsule drive, even though the Finder has no trouble opening it).
I then tried to re-select the Time Capsule as the backup disk. It asks for a password. I give the password and after a little while it comes up with the error message: Keychain error -25299 occurred while creating a System Keychain entry for the username “<name>” and URL “afp://<name>@2%20Tb%20Time%20Capsule._afpovertcp._tcp.local./Data”.
(where <name> is the name of the logged in user) I get the same error message independent of whether or not the logged in user is an administrator. Despite saying that it wasn't able to create an entry in the System Keychain, Keychain Access shows that there is an entry with the correct password. Also, despite being unable to select the Time Capsule as the backup disk, it mounted and left on the desktop the Data folder (containing the sparsebundle) from the Time Capsule.
Any suggestions?