Windows File decryption fails after PC reset

I have some Files which I saved in an encrypted format on one of my drives. Last week I did a full reset of my pc and now I wanted to access those files. Sadly I cannot decrypt the files anymore.

I tried to: right-click the file => properties => advanced => uncheck "encrypt contents to secure data" => ok => apply.

and then I get this error message

I did the encryption a while ago, so it is possible that I do not remember all the steps correctly, but it looks to me as if the reset of my PC lost the key.

Solution 1:

You've reset the OS, so the encryption keys are now gone.

You have to either:

• Restore the files from an unencrypted backup, or
• Restore the OS from backup and decrypt your files, or
• Import the certificate if you have it backed up