The iOS-EWS (device EWS) has stopped processing patches. According to <https://webkit-queues.webkit.org/queue-status/ios-ews> the last patch that was processed was 5 days, 20 hours ago (today is 12/28/2018). There are 66 patches pending as of the time of writing.
The corresponding bots (ews108 and ews109) seems to be down for some reason. More details in: <rdar://problem/46992643>.
bots (ews108 and ews109) are up and running again. iOS EWS queue is being processed.