[TYPO3-english] Access denied when trying to upgra from 6.2 to 7.6

[Jeppe Donslund]

After uploading files from TYPO3 7.6.2 I go to site.tld/typo3/install.
I have no problem logging in, but if I click on Upgrade Wizard, I get an almost blank page with the text "Access denied"

Is it a bug or what?

I have checked file permissions, they should be okay.