Ah, I missed that there’s already an update pushed for this. Thanks for the info @adutchman. I guess we just need to wait for it to propagate through the LG store.
I’m having the same issue.
Adding my name on the list too… Just happened today, 3 WebOS LG TVs 
Same here on my LG 65" , loads everything but only shows 3 dots when selecting something to play.
I’m having the same issue. xplay works very well
+1 on the LG brigade. As mentioned elsewhere, going via Photos & Videos is a temporary workaround.
Mine won’t work either, adding my name to the list
Me too … It`s look like end of the World - Plex stop working, so I want to play a game on Xbox a there are party bug on the servers from yesterday (mute bug) … so what now? I have to go out into the streets and pillage 
Same issue. adding my name to the list.
Same issue here. Worked yesterday, but not today. Would be great with a fix.
Thx Plex 
Yep. Same with me
How long does the update take to propagate to the LG store?
Same issue. Just 3 dots.
Same here.
Same here, although my TV is reporting version 3.13.16 in the Plex app …
@“waynesworlduk@icloud.com” said:
Yep. Same with me
How long does the update take to propagate to the LG store?
The updates to the Plex for LG app do not come through the LG store. They are pushed directly from Plex. I’m not sure if there is any way to force the update to happen.
It looks like Plex posted another update for the LG app today.
https://forums.plex.tv/discussion/comment/1651609/#Comment_1651609
April 11 2018 • 3.13.16
This is a release for only LG webOS devices.
FIXED:
webOS: Correct 3.13.15 video playback regression for webOS 3+ displays.
Now if I can only figure out how to force my TV to update to this version.
I also have version 3.13.16 now, was 3.13.14 a few hours ago.
The problem is fixed for me now and plex on LG can play videos again!
update
now seems to working again on my tv. i haven’t updated or reinstalled anything, so it’s a bit of a mystery.
I have the same issue happened just after plex update, three dots no play of any content. LG TV.is this matter being addressed and how soon will it take to resolve, love the product, but unable to utilize main feature. Please fix this issue quickly.
Confirmed here. Working now as well. App version didn’t change, but I did have to uninstall and reinstall the Plex app.
working here now app version has updated.