Never had an issue with Google Sitemaps before, but now it says i am no longer verified and i have to add a meta tag or upload a file. When i do this and try to verify my site i get a: We encountered an error looking up your site's domain name. We tried to access your verification file, but were unable to access your domain due to a DNS error. This could be because your server is down, or there is an issue with the DNS routing to your domain. Make sure that your domain is resolving correctly and try again. I see no loss of traffic to my site, and it is up?!? (i even see google bot visit just an hour ago in the logs)
The same is happening to me also. This happened a few months ago as well. The problem is on Google's end, nothing to worry about.
saw the same problem a while back. however, when mapping out a subdomain, it might take a few days for some reason until it can find it