Hello Lo,
The error message indicates that the file simply is not an AxCrypt file – it checks the first 16 bytes for a unique value.
Most often, this error occurs because the file is not produced by AxCrypt, but rather a different kind of file accidentally renamed to end with .axx. Another scenario is that it is a left-over after a previous decryption was interrupted at the stage where the original is overwritten.
If you mistakenly rename non-AxCrypt files to end with .axx, in which case renaming back to its appropriate extension will fix the issue since the file was never encrypted in the first place in this scenario.
Still, you are not able to decrypt the file, AxCrypt provides a feature called Try Broken File. You can decrypt the corrupted AxCrypt encrypted files by navigating the menu File | Options | enable Debug from the AxCrypt app.
Now you could see the Debug the menu in the AxCrypt app. From the debug menu choose Try Broken File.
Then you will be prompted for file selection. Select the corrupted encrypted file and then AxCrypt will try to decrypt the file. If successfully decrypted, then you can see the decrypted file in the file location.
Unfortunately, If the file is actually damaged to this extent, sorry to say, no, it can’t be fixed. The data is just not there to decrypt it.
Still, you are facing any issue, please provide detailed information about the issue and write a mail to support@axcrypt.net. We are happy to help you.