I just updated our Domino server (on Win2k8) to 9.0.1 FP4 and Traveler to 9.0.1.8, along with created a new self-signed certificate for the Traveler users. This was all prompted by the iOS 9 change (and soon to be everyone) to TLS from SSL. The upgrade for both Domino and Traveler went as smooth as they ever have. The self certification process a bit less so, due to IBM's documentation habit of linking you through 8 different wiki pages for one issue.
So, all that was finally done and working fabulously!! We had a number of recommendations from Heather at RPR Wyatt on some best practice configuration changes. Again, all that went just fine.
So, immediately I started seeing the following error, but only for two Android users:
11/11/2015 01:40:57 PM Traveler: SEVERE [Android_] There was an issue sending the notification message to the...