Missing Files
protected static readonly string[] mazeMapPaths = new string[3] { Path.Combine("..", "..", "..", "maps", "maze512-1-6.map"), Path.Combine("..", "..", "..", "maps", "maze512-1-2.map"), Path.Combine("..", "..", "..", "maps", "maze512-1-9.map") };
protected static readonly string[] scenDirs = new string[3] { Path.Combine("..", "..", "..", "scen", "scen-even"), Path.Combine("..", "..", "..", "scen", "scen-random"), Path.Combine("..", "..", "..", "scen", "scen-omri") };
The main set of maps and problem instances (scen-even and scen-random) is the standard MAPF benchmark, which you can find on mapf.info. Place them in the appropriate relative path once you download them.
The scen-omri folder isn't required. It's an extra set of problem instances generated by @OmriKaduri. Perhaps he can provide a link to them.
Please let me know if this resolves your issue.