The extension works fine on all pages until you close out of the welcome screen that shows up on first install. I find this behavior quite odd.
37
Raindrop extension doesn't stay signed in
2 months later
- Edited
While my Raindrop page was open I went to Tools in the menu and chose compatibility mode and the plugin opened to bookmark the page I wanted as expected. It seems to work whether you have the plugin from either store - my preference is the Firefox simply because it is in the blue colour like Raindrop and the Chrome one is a white cloud.
Edit - it worked about twice then reverted to the previous behaviour.
18 days later
Upvoted and following, raindrop.io and notion (also mentioned here and in a separate issue) are extensions I'd love to have access to.
a month later
please add support for raindrop.io 
To get Raindrop working, you have to disable the Tracking Prevention feature in the menu bar, under Develop. This is a massive shame, as privacy is one of Orion's best features, but I expect this also means the solution to this (and likely many login-persistance issues with other extensions) can be easily fixed by whitelisting some tracking essential to common extensions. In the meantime, disabling Orion's built-in tracking prevention and downloading a third party alternative that gives more granular control (uBlock, Privacy Badger, etc) will, I hope, do a similar job. Hope this helps someone that is as reliant on Raindrop as I am, and helps the Orion team expand their extension compatibility 
Ryan-Smith You don't need to disable tracking prevention to gain access to use the plugin. Browse to app.raindrop.io, click on the gear icon, and select compatibility mode. This will disable tracking prevention for the site. You will still have to authenticate once a session, but for me, this is just a matter of closing the browser window that opens.
Best bookmarking extension.
Dosen't work properly in Orion.
Shows me as signed out, but when I click on sign-in I am clearly signed in already
Same thing with all the Pocket extensions. Doesn't matter how many times you sign in, they never work.
Merged 2 posts from Extension raindrop.io bookmarks.
We are aware that these extensions (raindrop, Pocket... ) do not stay logged in.
19 days later
"Be sure that Browser Privacy setting is Standard
Go to Settings -> Privacy & Security
Select Standard for Browser Privacy setting
Be sure that **Firstparty Isolate Mode is turned off**
Open new tab and paste about:config into address bar and press Enter
Paste privacy.firstparty.isolate into search field
Set value false for privacy.firstparty.isolate
Restart Firefox
If you using Firefox Containers try workaround mentioned below""Be sure that Browser Privacy setting is Standard
Go to Settings -> Privacy & Security
Select Standard for Browser Privacy setting
Be sure that **Firstparty Isolate Mode is turned off**
Open new tab and paste about:config into address bar and press Enter
Paste privacy.firstparty.isolate into search field
Set value false for privacy.firstparty.isolate
Restart Firefox
If you using Firefox Containers try workaround mentioned below"For the record, I re-installed the raindrop extension the other day, and have been testing it a few days, and it seems to remain logged in and functional at this time.
Anyone else?
2 years later
This is still an issue, I get logged out every few days, less than a week. And it happens on multiple machines.
14 days later
For me this is also a persistent issue.
tchekz What did you mean with this post, did you adjust some settings in Orion and had it working?