It looks like you might be trying to load a TMX file as the Object Types Xml file. I suggest using SuperTiled2Unity instead which does not require an export step.
If you really want to stick with Tiled2Unity then try the following …
- Press the
Clear Object Typesbutton on the exporter. - Select
File -> Open Tiled File ...on the exporter to make sure you are loading a Tiled map file.
Note that Tiled2Unity is no longer supported and may not work against newer versions of Unity so even if you make it past the export process it sill might not work. Again, SuperTiled2Unity is the way to go here 