Sounds like a DNS propagation or some local issue. Try contacting your service provider.
My site is also showing this. https://myantworld.netlify.app/
How do I fix it?
Hi, @BlueTeck. Normally the only reason you would see an SSL error for a netlify.app subdomain is because of an ISP or other system (like a wireless router) doing something known as “DNS hijacking”.
This is more common than many people imagine and there is more information about this here:
https://en.wikipedia.org/wiki/DNS_hijacking#Manipulation_by_ISPs
To determine if this is the root cause, the first step is determining what IP address is returning the invalid SSL certificate. If you tell us that IP address, we can tell you if this is DNS hijacking or not. I can tell you in advance, it is almost always DNS hijacking that is the cause but, rarely, there can be other causes.
Would you please let us know what IP address is returning the incorrect SSL certificate?