ns1.signupsystems.com and ns2.signupsystems.com are CNAMEs to signupsystems.com. It is in principle forbidden to have NS records pointing to CNAMEs. (And don't forget the point of having two separate nameservers ;)
dig in +trace mode succeeds, because it does a complete resolve of the NS contents on its own. I suspect BIND9 is not able (or not willing) to follow a CNAME inside a NS, and hence some server in your local resolving chain is unable to locate your NSes.
Try removing the CNAMEs for the nameservers and add proper A records.
I could be missing something, but it appears to work just fine for me. I am able to pull both nameservers when digging for them off of the host name, and both are CNAMEs of signupsystems.com. One thing I did notice though, is that the whois name servers doesn't match the authoritative name servers. The whois gives the correct IP for ns1, but it lists 126.96.36.199 for ns2, which seems incorrect because both name servers resolve the same IP (the first one). If you try to do the lookup of your domain and it uses 188.8.131.52 as the name server, you won't get a response because that server appears to be down (at least not responding to DNS queries). I don't know what would use a whois record to find name servers, but I'd imagine this is where you're having problems.