It happens, one day the domain name just somehow don’t respond at all. Meaning when you typed it in the web browser www.domainname.com your name, nothing came up, it takes you to an error website messages such as not found, and when you check various whois tools and got mixed information, one site said it’s still registered, the other site says it’s renewed, so what’s going on? 1st try to contact your domain registrar or log into your domain registrar and see if there were any changes lately, look for recent changes. If you don’t have access to the domain registrar control panel. then you can check the domain by going to this website https://www.whatsmydns.net/ It is a domain name propagation status, basically it will checks whatever domain name you have and see if any web server or clients users can access it, you will either get a green or red. Red mean your domain is not visible on the internet. Green mean it’s visible, but you still cannot access it, then it’s probably web hosting server problem, or A records issue, not the domain name propagation problem.
Again, highly recommend this very useful website to check your domain name propagation process. https://www.whatsmydns.net/