Tagsistant uses FUSE which needs some special permissions to allow normal users to mount a filesystem. On most distributions there's a "fuse" group. Adding users to that group should be enough to allow them to use Tagsistant. On Ubuntu, i.e.:
# adduser tx0 fuse
Then logout and login again. Tagsistant should work.
If it still doesn't work, check the permission of the directory you want to place the repository in.