This time it does not appear to be a problem with their servers, but with their domain. The TrekCore homepage now reads:
You have reached a domain that was pending verification per ICANN rules but has since been verified. It may take 24 to 48 hours for the website to come back online.
Their Twitter feed notes:
TrekCore.com 🖖
If you're getting error messages when visiting our site, don't worry -- we're just addressing a bit of Omega molecule interference. As you know, when implementing the Omega Directive, all other priorities are rescinded....