Unable to login with admin

I am cannot access some of the shared folders on My cloud DL2100.
Using browser, I am able login with admin and can see the device and the share folders,.
Then using file manager I access the drive by \ip-address
A list of folders appear.

I can access public.
When I try to access backup it asks for the password.
Windows Security windows pops up for the credentials.
I click on use another account,
enter username = admin and password = xxxxxx (which i know works using the browser)

I get an error
\IP-address\backup is not accessible…may not have permissions (its admin so it should)#Multiple connection to a sever or shared resource by same user, using more than one username is not allowed …

What is going on here?

your help is much appreciated

Windows does not allow the use of mixed credentials when accessing network drives. You must access all shares with the same MyCloud user credentials.

Accessing the public share without entering any credentials, Windows will use your windows user credentials.

Unmap all network drives, then re-map the network drives, this time enforcing the use of your MyCloud credentials (“connect as other user”).

BTW, this is not the correct forum for DL users. There is a dedicated DL forum where you might get more specific answers in future.