The
Couldn't find region name 'Mycenae_reg' in string table
message should mean that it is missing, mis-spelt, missing capital letter (it is case sensitive) or has space instead of _ , or possibly space within {}, etc, somewhere in those files. Try changing all instances of it to 'test' or something really simple to check.

If that doesn't work, the fact that is the first region could be a clue, I've had 'can't build settlement' problems for first region in descr_strat, which seemed to relate to descr_strat being wrong format for RTW patch version, rather than error specific to region. You could have variation on that.

It sounds like you got it to load before, as you say putting land in med. worked, if so, what changed since then?