Server Error Preventing Validation


I have been trying to validate my site for some time:

I’ve attempted to submit my main page as well as various internal pages but I always get the server error message from the validator. Occasionally, I get a technical issues message. The the meta tags all look correct to me so the only thing I can guess is that my robots.txt may be preventing crawling? I’m stumped at this point. Can anybody offer assistance? Thank you.