I was basically asking if LibToSVN seems to be a regular SVN working copy directory, if so it would be e.g. recognized by the Tortoise tools.
If it's not, this would explain the error. Otherwise, there are different possible reasons as well. I would expect the said svn: E155007 message emitted by apache subversion (svn.exe) itself, not the Tortoise SVN shell tools. The subversion binaries are working behind Tortoise and the Altium library conversion tool. There may be e.g version incompatibilities or other non-obvious issues. I guess, you need to ask Altium support.