Check if there are any instances of Excel hanging in the computer's memory even after you close Excel down. This often happens with Excel. You can press Ctrl + Alt + Del to call up the Task Manager, then switch to the Processes tab and look for "EXCEL.EXE" in the list of processes. If it is there, close it manually and try again with MF Pro.
If it is not the case, please send me some screenshot showing what exactly MF Pro is saying when it can't find Excel (i.e. how you know that it can't).