The encryption process must always be deferred explicitly before shutting down the machine or rebooting. A warning is displayed about this during the encryption. This is important to avoid any data low caused by a sudden interruption of the encryption process.
That being said, interrupting the encryption can not cause by itself the password verification error: the encryption header is written during the pre-test and since it succeeded to boot after typing the password at VeraCrypt bootloader, the header was correctly
written to the disk.
At this stage, there are two possibilities:
- Something corrupted the hard drive part containing the volume header (very unlikely).
- You are just using the correct password.
In my opinion, the second possibility is the most probable. In some situations, people tend to forget or mix password content. In other situation, people make mistakes while typing in the keyboard specially if they don't use the "Display password"
functionality and when they try the day after they don't type the same keys and they think the day earlier the hit the same keys. It personally happened to me to mix 'e' and 'r', and also 'p' and 'o', when I'm in a hurry or not very concentrated.
If you had copied the rescue disk, we could check if this is the issue. Now, the only is to try to find the correct password by guessing what kind of mistake you could have done while typing it the day earlier.
I'm afraid no one can give you a better solution. This sad situation shows the importance of burning/saving the rescue disk before the encryption is fully performed.