When a pop-up is configured in AGOL to display date and 24 hour time with seconds, the time does not display in Collector. Time will display if set-up for 24 hour without seconds or using an AM/PM display with seconds. I have experienced this bug with previous versions of Collector with both iOS and Android systems. The current bug is with Collector 10.4.2 build 1026 for Android. I have not tested other versions at this time.