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Creating a 'Random_Maps' folder worked great!
Just remember not to have HoMM running when you create the folder, and if the game was still running, close it and restart.
If you have a copy of the game that works, copy the random_maps folder to the game directory that is not working.

Found this works just moments ago after the same issues for a long time

Hope this helps
Okay i have read all of these posts done everything that they have said and i still can only play campaign