Email confirmation fails with error in browser

I’ve tested the email confirmation and I click on the link in the email.

The link looks like this:

https://-WEBSITE-/wp-admin/admin-ajax.php?action=wpuser_activation&key=cLHKMqcrZZou&email=-EMAIL ADDRESS-

But this creates an error in the browser window that just says:

Invalid URL

——————–

This is clearly a problem