What software/device are you using to access SS?
There are apparently two servers, sip1.sipsorcery.com and sip2.sipsorcery.com. You can check their status by going to this
If you put either as your proxy, you will go only to that server. If down, you're just out of luck.
If you enable DNS SRV and give sipsorcery.com as the proxy, your software will query DNS for SRV records for udp/sip and sipsorcery will reply with both sip1 and sip2. Your software is then able to try either and settle on one which is working.
If you do not enable DNS SRV, you'll most likely end up connected to sip1, since sipsorcery.com and sip1.sipsorcery.com resolve to the same address.