The message “HTTPS Availability is being processed. Check back later”, appears for a long time due to an error in the domain settings on the domain registrar. But also because of errors during the configuration on Blogger.
This usually happens during the Custom Domain configuration in Blogger. First, after setting up the SSL domain, the website works well but later the site may be inactive. Also in Blogger dashboard you will see the message “HTTPS Availability is being processed. Check back later” for a long time.
But how can we avoid this mistake?
Domain Registrar: (if your website is down)
First, make sure you perform the correct DNS configuration in the domain registrar. If you are using Google Domains then things are simpler, and configuration is easier.
Add two exact CNAMES (not A Host or any other record) as you see on the dashboard blogger, similar as: