re: Hobolink. I think this software is messed up and caches DNS much longer than it should. I'd be willing to bet if your station drops out resetting the software will fix the issue. Software must respect the realities of the modern internet. We can not keep antiquated hacks in our systems to support badly written projects. I recommend speaking with the hobolink developers and asking them to make sure that your station does not cache its DNS record. WU ingest is working fine.
the main issues are
1) putting an IP address in as the send to location. These addresses are not static, you MUST use a dns name "rtupdate.wunderground.com"
2) caching DNS, if you do use a dns name, the software MUST not cache it longer than the TTL as noted in the DNS record.
This is basic stuff, but I have found many software packages fail on getting the above right.