what about SSL certification?

That's not a nicepage problem but they're not holding your sites hostage. Don't know if they have implemented support for to the free well-known SSL issuer (Let's Encrypt) https://punchsalad.com/ssl-certificate/install-lets-encrypt-godaddy/

Any decent self-respecting host should be offering Let's Encrypt. Pretty sure nicepage hosting does

That said, the first domain is available under http and works just fine (https doesn't) which means that one can use https BUT DOESNT ENFORCE IT.

The second one is only available under HTTPS

check your godaddy SSL / certificate settings and disable HTTPS / forced SSL redirect

https://www.godaddy.com/help/redirect-http-to-https-automatically-8828
https://webmasters.stackexchange.com/questions/68949/how-do-i-disable-ssl-on-a-godaddy-hosted-site
https://webmasters.stackexchange.com/questions/105106/prevent-https-forward-on-godaddy
https://www.godaddy.com/community/Websites-Marketing-Website/How-to-remove-HTTPs-on-My-Website/td-p/116162

That should at least bring the 2nd site back up under HTTP, allowing visitor access while you swap hosts.

Thank you! That was very helpful actionable information. I will be back to move my sites over to Nicepage, for sure.