Old Blogger to Google "User account not found" Problem Fix
If you use Blogger you probably got this message: "To continue, you need to sign in to Blogger with your Google Account. The new version of Blogger requires a Google Account to access your blog's features"
Some people are having a problem with a message "User account not found" when you try to migrate from one to the other. I have found that the problem is that it is case sensitive. So if it automatically says your user name is HappyDay, the computer may be expecting happyday. The way I fixed it was to look for your username in the URL which is what is bringing the name over in the user name box which is not editable. You have to change the caps in the URL and then hit enter. That worked for me, if my name was HappyDay, I changed it it happyday in the URL and entered that URL to go to the next page which then had my user name in lower case and the user name was found.