I can access my website from any vpn but many services show my website is down. How can I fix this?

My website, nclicker.mooo.com:443 on 94.193.235.194 is accessible but many websites tell me it is down or I can't connect to it. I am running a node js/express server on it and am trying to get a https certificate with LetsEncrypt.This problem also occurs with ports but 80 isn't accessible as it is blocked by my isp: Sky. I have also checked on websites like http://ift.tt/eYL7pc and it shows me my website is down.