This seems like there is some routing problem from CosmosEx to network through wifi. When you mention that most of the connections to and from CosmosEx work even through wifi, then I wonder if it's not just the routing related to the main app which has some issues (e.g. curl library inside of the CE linux app).
With ethernet cable removed and wifi module present, can you see if these work and give similar results as when connected only through cable?
If they do output similar things, then the routing is OK, and you can try to restart the CosmosEx main app (just in case the internal state of it has something with routing):
...and then see if you can see the software update version other than 0000-00-00 (but do give it like 30 seconds after starting the app to retrieve the sw version from server).