The update installer is located in "your account" section of the website. Download and run that installer, and restart your DAW.
Just bought Serum, doesn't show in Ableton.
Started by tonediggity
A Work-Around for Ableton Live not seeing plugins:
There is a bug in Live where sometimes no matter what you do a plugin will not show up.
One particular incident I can use was when I installed Soundtoys. Everything showed up except for Effects Rack. The work-around is to rename the dll. (for example; change "Effects_Rack.dll" to "Effect_Rack.dll" (removed the 's').
It's super dumb, but in some rare cases this might be the only way to get a plugin to show up. Not every user experiences this issue. It's a good work-around to try if all else fails. Do spend some time trying all the above first. Renaming files is not ideal. I told Ableton support maybe over a year ago, but who knows if they'll ever fix it.
The above is not really great advice.
Renaming plugins will lead inevitably to duplicates when running updates, etc. Duplicate plugins is the top support item right now.
It's not a bug that a DAW will quarantine plugins which crash on scan. Otherwise you'd be stuck there as a user. To be fair, Live could be more verbose about quarantines, like other DAWs do (Cubase/Bitwig) and you wouldn't think it's a bug.
alt-click on Rescan button in Live preferences->plugins will rescan blacklisted plugins, no need to rename files.
and/or you can remove the plugin, launch and quit Live like that, then put it back, and it will rescan.