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Problem solved.

I tried step by step according to this guide:https://support.sega.com/hc/en-gb/articles/11568479123857-What-should-I-do-if-I-receive-an-XML-error-message-when-launching-or-running-Football-Manager-

Finally I solved it during the last step:

Quote

If you're still struggling after doing the above, try as follows:

First of all, right-click on your desktop and select 'New' -> 'Folder'

Create a folder and name it something to distinguish it (say ‘SI backup’)

Once you've done this go to your Sports Interactive folder found within 'documents' which by default is at the following location - C:\Users\[YOUR WINDOWS USERNAME]\Documents\Sports Interactive\[Football Manager title]

This should contain folders like 'games', 'crash dumps' etc. Please cut every folder from here and paste them into the folder you've created on your desktop.

Once you've done this and the Sports Interactive\[Football Manager title] folder is now empty, launch the game. If it works, copy back the files from the desktop folder and hopefully it should now load without any issues. If the same issue re-occurs when you copy back, it may be something specific within those folders like custom files, so we'd suggest removing those. Remember, if you delete any save games from within these folders manually, they cannot be restored. 

I checked each folder, and found my problem in the editor data file. Here I had stored a folder downloaded from https://www.fmscout.com/a-fm23-leagues-pack-by-timo.html. There are so many single files in it with some invalid. After deleting the folder, the problem was solved. Also, the game works well if I only store the valid files directly under the editor data directory rather than under a secondary folder.

I think my problem was due to excessive invalid files in the editor data folder. Hope this will help.