As I indicated above / is almost always correctly interpreted as a path separator in Windows programming. The only context I know where ‘\’ is required is on the DOS/PowerShell command line or in .bat files.
The suggestions above (using raw"..." or \\) should work, but are almost certainly irrelevant to the OP. It seems likely that some of the reputed problems are a result of syntax errors, not of the function call itself. This also applies to the replies to Problem with Weave Code, also started by @brett_knoss
It would be useful if @brett_knoss could provide not only the code used, but also the context (what is expected to happen here, what actually happens, what are the relevant input files) as well as the error messages that result.
The second and third points suggested by @tlienart are probably the relevant ones to address.