Cornhoff, open the map with the editor.
Edit map properties and select all heroes.
It is possible that some spells are banned so do the same for the spells.
Save the map and try again.
@Jorajan, I am sorry but we do not support or fix scripts of third party maps. Unfortunately there is too much things to work on and too less time
However if anyone takes the time to make them compatible with MMH5.5 we will gladly advertise his work.