V146 always showing that it needs to be installed. The file DL's but Twitch keeps stating I haven't updated it. Is this a known twitch issue or issue with BigWigs? TIA

this is Twitch's problem, actually update success

right click delete and reinstall bigwigs will be fine.

We have no control over Twitch issues unfortunately.
As already advised, I would try deleting and reinstalling.
Also if you have PTR WoW installed double check that Twitch is set to update the addons on live not PTR.