Time Machine will no longer connect to backup disk

what's going on?

Let's find out. We assume that you have already performed the basics like powering off the Time Capsule, restarting your Mac and then powering the Time Capsule back up again.....correct?

Hold down the option key on your Mac while you click on the Time Machine "clock" icon at the top of the Mac's screen. Select Verify Backups and run the check. The process might take anywhere from a few minutes to 30 minutes or more depending on how much data is contained in the backup files.

You will be notified when the Verify Backups check is complete. If you see any error messages, post back with the exact text of the message.

The "problem" is that the backups are corrupted and are no longer useable.

You will need to erase the Time Capsule disk and then start over again with a new complete backup and move forward again.

Post back if you need instructions on how to do this.

However.....if the Time Capsule is 7+ years old, I would not trust the device as your sole backup plan, since the Time Capsule hard drive is suspect at this point.

The Time Capsule is both a router and a hard drive. If you replace the Time Capsule, will you also need another Wi-Fi router.....or......are you already using another Wi-Fi router and are using the Time Capsule simply as a back up device?

Good news that the TC is backing up again.

Since the TC has a USB port, can simply plug an external hard drive or SSD into that port and use it for Time Machine?

Yes, if the hard drive is formatted as Mac OS Extended (Journaled). But, the Time Capsule uses an ancient USB 2.0 port, so backups are going to run at about half the speed of normal backups to the Time Capsule disk. The port also may or may not have sufficient power to run a USB hard drive that does not have its own power supply.

If the Time Capsule is 6-7+ years old, the power supply is also suspect at this time, which might be a consideration.

The simplest, fastest, cheapest and most reliable way to back up would be to connect a USB drive directly to the Mac.

If you want to back up over a network, then you would want to look at a Network Attached Storage (NAS) device. Synology would be an excellent...but expensive....choice. More info here:

https://www.synology.com/en-us/support/nas_selector

The good news about backups is that most users don't even notice how long backups take to occur, unless there are problems with the backups.

Newer Mac operating systems.....(I can't remember which one introduced the new options)......allow you set up Time Machine to back up once a day rather than every hour, if that might help things.