I received a validation error message and the fields were cleared. Then I pressed the browser's back button and tried again. But got it wrong again.
I enclose the file that works "registrering.php". As well as the two files (the form and the thank you page) that I do not get to work.
Note that I have only entered validation on the first field to test. The result is that the error message is displayed in black and with the wrong class "serverInvalidState", instead of "invalid-feedback". I also attach screenshots of this.
I also notised an error from crome, see screenshoot.