VeraCrypt volume does not decrypt - lost the password. Error message: "Source: MountVolume:8299"
Not being a professional cryptographer you have no chance to decrypt your VeraCrypt encrypted volumes — if it would be possible, the VeraCrypt encryption would have no sense, have it?
Fixes that you read and tried are absurd in the context of my previous sentence.
Even a professional cryptographer would have no chance without other supporting information, if your forgotten password was strong enough.
How can I use the 'Restore volume header' function if it requires the password?
Again, you have no chance without the correct password.
VeraCrypt is not a toy, it's a serious encryption tool, open source, without some obscure tricks you are able to reveal.
Answers to appended text in your question:
If others have been able to successfully open ...
No, they not been able. There is no evidence. (There is a difference between claiming they did something and really doing it.)
Follow me:
- Did renaming a file change its contents?
- Did copying the file to another location change its contents?
- Did running VeraCrypt in Administrator mode change the file contents?
VeraCrypt encrypts / decrypts only an encrypted file container contents, irrespective of its name, location, or user privileges. User privileges may only allow / forbid the read / write access to a file, without changing the way how VeraCrypt will process it.
... then maybe Veracrypt isn't stable or reliable enough to place valuable or important files in its encrypted file containers?
VeraCrypt didn't care about value or importance of your files, it simply encrypts whatever you want.
In some very rare occasions an encrypted file container may be damaged, of course, but then renaming / copying / using Administrator rights will now repair it.
If there's such a thing as the volume header getting corrupted and one has to do a 'restore' to successfully open the file ...
The volume header is crucial for decrypting / encrypting the encrypted volume file, so VeraCrypt stores its copy in another place of the encrypted volume file. "Restoring it" means simply copy it back to header. But because this copy is encrypted, too, you need a correct password to perform this operation.
Does a volume header getting corrupted prevent the decryption of a file container?
Yes, it will prevent, as I already meant. But you may restore it from the (hopefully uncorrupted) copy of it — if you know the correct password.