Time machine: seem to be able to make a backup but cannot access it

I  am able to make a backup from my imac to my WD 4 TB with tim machine.

But is is impossible to acticate time machine from my imac.

I have a mac mini that also makes time machine backups. this one does work to my WD and I can acces the backup.

What is going on? 

Is the WD nas compatible with time machine or is it only a half sollution?

I need to know, because now I cannot access my file when I really need to!!

HELP

Are you having problems with Time Machine only?

What happens when you try to activate time machine.

I’m a bit confused since you stated you CAN make a backup with Time Machine but then you can not activate Time Machine :confounded:

The fact that you are able to do backups with a different computer shows that the NAS is compatible with TM.