"Couldn't create the playback session for this item" error on iOS devices

Stemming from https://forums.plex.tv/discussion/213460/deleted-friends-still-able-to-stream#latest that happened today. However, different topic; new thread.

iPhone 6S:
Device model: MKT92LL/A
iOS software version: 9.3 (13E234)
Plex app version: 4.0.15

iPad Air:
Device model: MD785LL/A
iOS software version: 9.3 (13E237)
Plex app version: 4.0.15

Brief description of the issue or bug: When trying to play video on Plex app, I receive the following error message: Uh-oh! Couldn’t create the playback session for this item.

Steps to reproduce (these will make it easier for development to track down): Play a video.
When the issue has to do with information from your Plex Media Server (such as streaming content, accessing item details, creating playlists, etc.), you should gather the “Plex Media Server.log” file covering the issue being reproduced and - attach that to your post. Log is available via PM if needed.

This is happening on both iPad and iPhone 6S. Also, please see other discussion. Perhaps something was changed internally at Plex.

Also, other devices are working; LG Smart TV, PC, and Mac web browser all steam fine.

Is there an update that the devs need to apply soon? Please let me know if you require further information.