DIR command returns Bad file name or number error

Hi,

I have a few lines of code which check to see if a file exists on our sharepoint and then if it doesn't it gives a message and closes the macro or if it does exist it opens the file. I get a run time error on the DIR part of the code. The workbooks.open code works fine on its own so the file path is ok. The DIR part of the code does work if I first go into the sharepoint and open the folder, then the code works fine. Then if I close excel and re open the code doesn't work again. Is there an alternative I can use instead of DIR to find out if a file exists or another idea? I've replaced the actual sharepoint file path with the words sharepoint address and folders etc

Dim Pablo_Sourcer_File_Path

Pablo_Sourcer_File_Path = "\\sharepoint address and folders etc\Tracker.xlsx"

if Dir(Pablo_Sourcer_File_Path) = "" Then
msgbox("File not on sharepoint")
exit sub
end if

workbooks.open Pablo_Sourcer_File_Path