First TripleA Game Test
Ok I don't think we had that issue before, but the error message is pretty unclear.
In order to fix that I created a Pull Request https://github.com/triplea-game/triplea/pull/4964
Once that gets merged you'll have to download a new pre-release version of the game and try the same steps using that, it should provide a better error message.
@Viking Please install https://github.com/triplea-game/triplea/releases/tag/1.10.15187 and try posting using this version.
Feel free to install it in another folder, because it's incompatible with 1.9.X versions. The PbF/PbEM Settings moved to the Settings for the most part, so it might look a little bit different, but for the most part it should be the same.
If the error still happens there (which should be the case), it should at least provide a better error message that will hopefully lead us in the right direction