The errors "CantAddRoot" or "CantSyncRoot" may occur if the catalog file is in a read-only mode (or stored in a write-protected folder, for example, in the WinCatalog folder in Program Files).
The screenshot below was reproduced by running WinCatalog as administrator (just after the installation), creating a new catalog file inside Program Files folders, and then restarting WinCatalog with the normal rights and trying to add a disk:
To solve the problem, please try to copy the catalog file into another location, for example, into Documents folder, or create a folder called "My Catalog" on drive C:\ and copy the catalog file there.
To ensure that WinCatalog does not have writing rights to the catalog file, please perform the following experiment: please run WinCatalog and try to add a virtual folder or a custom item by clicking one of the following buttons:
Were these items added to the catalog? If you cant add these items, simply moving the catalog file to another location should solve the problem.
Otherwise, please enable the debug logging and send the log file to us for the investigation, we will do our best to solve the issue.