Unable to use MyCloud with iMac's TimeMachine

when opening Time Machine preferences -> Select Backup Disk -> TimeMachineBackup, I got error looks like below:

The disk image “XXX’s iMac.purgeable.sparsebundle” is in use.
Try ejecting the disk image.

I tried to reboot iMac and MyCloud as well, as suggested by some from online, it didn’t work.

Any ideas?

Hi there,

You can try this may it would work-

Thanks for your response. However I didn’t see the on/off toggle button on the timemachine preference setting, as what was in the article that you indicated.