This is going to be a silly question, but is not meant to be offensive. Can you check the about:preferences#sync page to see if the Add ons option is checked to be synced on each of the devices that are logged in?

No worries. Actually, your question provided a solution to my problem, but it also makes me question why it is acting this way. So let's say I have 1 work laptop, and 2 home laptops. I want to sync history and tabs on all, but I don't want to sync extensions to/from the work laptop. Is this supported? I believe so, but here's the rub. ATM I only have 1 of each, so again, the work addons box was clear. The home laptop had it checked, but I had to reinstall FF because of some sort of error at launch. I never untoggled addons when I uninstalled, so it seems like it should still reference my sync settings in my FF account. Anyway, it didn't, and my work laptop wasn't checked, so toggling that fixed it to an extent, but I have different extensions installed so it helped, but not entirely. Hoping for some insight as to what i'm missing, but at least I have an answer of sorts and I much appreciate that.

Hi urntoc, Great, that clears up some possible issues and you are really onto something.

The feature for those settings are going to be all or nothing, an alternative might be to have a different account for the device that should have certain addons, I hope that makes sense.

Also, you mentioned extensions, here addons are extentions in the about:plugins page however there will be no plugins that will sync.

Are the addons that are not syncing flagged as "some extensions could not be verified"? That might be it if you have different versions of Firefox on each of the devices. (47or 48 is where unverified extensions/addons were stopped from being synced)

They're not flagged and I was probably a bit sloppy in my Mozilla-speak. It's the extensions toggle, and I'm talking about those EXTENSIONS that are installable via ADDONS.mozilla.org. I think that causes some confusion, to be sure, but thankfully you've understood me correctly from the get go.

I have considered different accounts, but I cross between the devices enough that I really need the history and tabs across all of them - just not the extensions. Anyway, there are bigger issues in the world, I know. Thanks again for your help!

I added the verbage to the list of things to suggest changing for context in the community discussion. I hope that straightens it out. Sorry for my confusion.

Did you get the add ons to sync? Would be possible to share the name of one that is not syncing in order to troubleshoot further?