Home Forums Mac Software Mac Operating Systems TIME MACHINE does not recognize backup

I have used Time Machine to backup my desktop. No problem. I can enter Time Machine and retrieve/restore any file. No problem.

What just happened today, however, is that that when I click on Time Machine TO DO a backup - manual backup, not automated - the backup disc cannot be found on the Time Capsule's drive. It IS there because I can retrieve files from it; but the drive is not found when I wish to do a backup. It also no longer appears in the Select Disc tab of the Time Machine menu.

I know the backup contents are still on the external drive, I just cannot back up to it.

Any ideas?

i.e. iMac/Mojave/Time Capsule/Time Machine/Wi-Fi