Hmm...I think I see what you mean.
Here is an example of a share of mine (names removed, its a corporate list, sorry).
Now, you feel you should be seeing sub-folders under the root shares. I believe that is a Windows limitation here, that this browser window Veeam is using cannot drill down below the root share of a server. No fix there tho...
Also, Vitaliy asked about typing out the path. If you enter the complete UNC path you are trying to get to instead of browsing, does it (a backup) work successfully?