Edited for correct version

Installed 2.16.3 via Twitch/Curse from update 2 hours ago.
My WA frames no longer show and I cannot open /wa or /weakauras
Reloaded UI, restarted client, did not help.

I uninstalled, went back to version 2.16.1 from 2 days ago, and it worked.

Try 2.16.3

Correction: 2.16.3, not 2.16.2 which I was using earlier today, is actually the issue. Sorry I had a digit wrong. I just now corrected the title of the ticket.
To be 100% safe i went back 2 versions to 2.16.1 from back in January 17 and that worked.
To be 100% certain I just went back and installed the new 2.16.3 from 2 hours ago and it does not work as I described, and 2,16.1 does. I haven't tested 2.16.2, but i assume it works because that's what I was using earlier.
I understand the WeakaurasArchives is being added in maybe this version, and that's causing the error? Or maybe wrong code was pushed to Twitch? idk tbh
I'm assuming no one has said anything here or MMOC because it's late in both in Europe and US

Yes, I'm getting a bunch of Couldn't open WeakAuras\Libs\Archivist\Archivist.xml and Error loading WeakAuras\ArchiveTypes\Repository.lua errors. Along with

2x WeakAuras\WeakAuras-2.16.1.lua:1547: attempt to index upvalue 'Archivist' (a nil value)
[string "@WeakAuras\WeakAuras.lua"]:1547: in function `OpenArchive'
[string "@WeakAuras\WeakAuras.lua"]:1562: in function `LoadFromArchive'
[string "@WeakAuras\WeakAuras.lua"]:1582: in function <WeakAuras\WeakAuras.lua:1578>

[string "@WeakAuras\WeakAuras-2.16.1.lua"]:1734: in function <WeakAuras\WeakAuras.lua:1685>

Edit: A relaunch seems to have fixed this (for now?); I'll pop back if it happens again.

Always restart the game when updating addons.

Pretty sure the game wasn't running when I updated it the first time, but I could be mistaken.

Same problem here. Latest working version is 2.16.1. Tried updates till 2.16.5 and all they cannot work.
When login account, WA is automatically paused process, need to hold 'Shift' + 'left mouse click' on the mini maps WA button. And /wa or /weakauras cannot open WA options.

Same advice, you need to not have the game open while updating addons.

Game wasn't running when getting updated.

Then create a new ticket and pay attention to the questions that get asked. Especially those that ask you to run with bugsack/bugrabber enabled.