I can not add my website to the panel.

After trying I can see the message: “We could not find your new website.
Please make sure you have followed steps above.” I do not know why. In the panel of Wordpress have already installed WPMU Dashboard and everything works (Plugins and themes). Admin address: https:// Please advise. Thanks
Oh I forgot to add that I have successfully installed already two other websites. I test the plugins on them. That site, which I can’t add, It has to be the right one.