iMac will no longer backup to Time Capsule
My iMac (mid 2011) will no longer backup to Time Capsule. The message I get when trying to manually start a backup states "Backup Disk Not Available" The details button states: "The backup disk could not be found. Make sure the backup disk is connected or select a different backup disk." I checked the connections and they looked fine. It gives me an option to remove the existing disk (which I have been using for backups and which it can no longer "find") or set up a new Time Capsule that is not listed. How do I fix this and why did it stop backing up in the first place? I've had the Time Capsule since 2012.
iMac, OS X Yosemite (10.10.5)