backup mac on external hard drive time machine not working

I waited 24 hours and when I went into TimeMachine there were about 20 successful hourly backups waiting for me. Wait for a while to confirm that subsequent backups have also completed successfully. Start up Time Machine, remove your existing backup disk selection (especially if it is the disk you were just erasing), and re-select the external WD disk you just did First Aid on as your backup disk. Again, if your results differ, talk to Apple. This was also very quick and also ended in a green checkmark. With the external WD drive still selected, click on First Aid and say OK to erase disk.

Pick a name and you want to format as “APFS” (not encrypted or case sensitive) with GUID Map.

Select the External WD disk you want to use for backup and click on Erase Disk (presuming you want to use the entire disk as your backup - if not you’ll need to call Apple for different directions). I don’t know what you should do if your results vary. For me this took 4 minutes and ended with a green check mark that everything was fine. Select your primary disk (usually Macintosh HD) and click on First Aid. It looked to me like the same Disk Utility you could get at without Repair Mode but you have to be in Repair Mode. Once in Repair mode, you will be shown a list of 4 choices. Get into Repair mode by powering down your Mac, then immediately after pressing the Power button to turn it back on, press and hold Command-r (⌘+r) for a while, until the Mac does NOT show a booting scroll bar, but instead asks you a question or two like “Language?” Note you must power down, not just Restart, since you can’t do Command-r fast enough during a Restart. Steps Apple Support took me through to fix this: My setup: A new (2019) MacBook Pro 15' running Mac OS Mohave (10.14.5) with a new 4TB WD My Passport. I had my first complete backup yesterday, and about 20 successful hourly backups since then. It took 3 calls to Apple Support, but they have solved it for me. I had exactly the same problem - no matter how many times a I rebooted my Mac or reformatted my WD drive, the first Time Machine backup would succeed and any subsequent one would fail with “Error occurred while creating the backup folder”.

Backup mac on external hard drive time machine not working