Hi there, the issue is generally in the DNS setup at your domain hosting provider. You could try to change your dns setup, so that the two domain A records you have setup, are pointed to the IPs that you have listed, and for host, put both to "@".
In the sub-domain boxes below, make the host column just "www" and then check that the proxy.webflow.com entry is correct, it looks like you have an additional period in there, but not sure if that is just how it is listed in your domain control panel setup for namecheap or if you put that period there.
Then after you make the updates, go and check your custom domain hosting setup in webflow. Add the mydomain.com entry first, and then add the second domain www.mydomain.com. Save changes.
If everything saved ok in your domain control panel at namecheap, and the dns server changes have propogated, then then your domain should be pointed at webflow servers, and you can check status to see if the changes have been updated successfully.
If that still does not work, then you might try to contact to your domain name provider, and ask for some assistance. Basically, if the DNS changes are somehow NOT made successfully to point your domain (which webflow does NOT control), then there is nothing to tell the DNS server at namecheap that your domain needs to be forwarded.
You can check if the DNS server changes have been updated using the following link... just put in the domain you want to check on in the search box, and click search. The result will show, from around the world, which servers are pointed at the correct webflow servers, and which ones are still pointed at your original DNS name servers.
If you still need some guidance, please feel free to PM me. Sometimes it can take a little wraggling with different DNS providers to get it configured correctly. Sometimes it also depends on the type of domain you have... if you are using a top level domain (.com, .net, .org) domain, these changes are usually propogated faster than other kinds of domains, such as .io domains, which can take a longer time to process in some cases.
Hope that helps and feel free to contact me via PM for further help if this problem continues for you.