On the off chance that anyone else has run into this issue, I thought I would ask.
I own Live 9 Standard and bought Sampler and Operator separately years ago. When I look at the upgrade options for Live 10, the only version that includes either instrument is Live 10 Suite. If I upgrade to Live 10 Standard, not Suite, will I still have access to Sampler and Operator?
If you’ve run into this issue how did it work out for you? I’m impatiently waiting to hear back from Ableton. 
It should still work! When you buy separate instruments from Ableton website, they fall under the Packs category. You may just need to reinstall each from your Ableton account, or reinstall from the Packs section of the Live Browser 
Oh I see! Hmmm. Interesting. Sadly I can’t install them to Live 10 Lite. I get a license-related error message.
Upgrade your 9 Standard license to 10 Standard to see Sampler and Operator.
So you’re saying that if I upgrade from Live 9 Standard to Live 10 Standard I’ll still be able to use Operator and Sampler?
That’s quite strange, on the page here it says it only requires Live 9 Lite or higher:
https://www.ableton.com/en/packs/sampler/
Did you happen to buy it under a separate account by any chance?
I did exactly this during the Black Friday sale, was in exactly the same predicament as you (Live 9 standard owner, who bought Operator and Sampler separately). Upgraded to Live 10 standard and all was well - no problems whatever. 
As long as it’s the same Ableton account you’re using, yes. if you set up a new account to try out Live Lite, then Sampler & Operator won’t be linked to that account, which might be why they’re not showing.
EDIT: Ableton has confirmed that Sampler and Operator should work with Ableton Live 10 Lite! Woo. I just can’t get the licenses to cooperate. I keep trying to authorize using the “Authorize” function on my Live 9 License page and it won’t work. Hmmmm…
Do you recall how you installed Sampler and Operator separately from Live 10 Standard? The authorization is failing every time I try to Authorize from my Account.
In my Ableton account I have the choice to download packs, free and purchased after log in. They should be available in your account via packs downloads. It should say “purchased, or similar” regarding those packs which should include the authorization by default… I think 
That gives me the option to Authorize, but not download, Sampler or Operator. Unless I’m being dense, which is entirely possible.
Have you tried installing directly from the Packs section of the Live Browser? That’s usually how I download my packs/instruments.
Yeah, that’s what I did, authorised them - and they were available to use through Lives browser.
Thanks, all. Ableton had to move the instruments from under my Live 9 Standard license to my Live 10 Lite license.
Good thing I’m not as dumb as I thought I was. Am. Something.