This exact problem is happening to me too right now (March 3rd, 2020). I'm also on "worldnic" name servers from network solutions. So you're probably affected by the issue being discussed in the thread below, where for some reason LetsEncrypt can't get valid DNS responses from our DNS provider. All seems related to web.com/networksolutions.com/register.com which all tend to use these "worldnic.com" name servers.
I'm planning to move away from NetworkSolutions for many reasons, this is just the icing on the cake; they seemingly are blocking LetsEncrypt datacenters from querying your DNS records. I'd rather not have my DNS provider decide who can query my public name records.