Login Register issues

Login page is leading now to standard wp login and by register ist in red to see:

ERROR: The username field is empty.

ERROR: The password field is empty.

But fields are not to see. I don’t know what to do 🙁

I parallel get an google failure about not possible to index

https://rainbowsongs.org/complete-registration

because of fowarding

The page I need help with: [log in to see the link]