If you can't open your file, please try to find your backup file from File Cache.
Please note that only 9.1.0 or later version supports File Cache.
Please follow these steps to recover the file.
1. Launch XMind: ZEN,
2. Enter File > File Cache,
3. Find the file you need and select Retrieve.
If you cannot restore your file there, please send your corrupted XMind file to firstname.lastname@example.org. We will try to fix your XMind file on our side.
Please note that if your file has become 0KB, we can not fix it.