Worked fine until 2.17.0 where i cannot connect to specific country because keeps loading forever.

Also the release notes "Updates and Fixes" are not very helpful. ;-)

App not working properly
After a day working, started asking to re-enter my credentials every time, which are rejected from NordVpn server. It happens with Firefox but not Chrome.
Reinstalled extension. It was recommended as a solution: RC on the extension icon > manage extension > scroll down to Run in Private Windows > allow. I don't know why they want this permission if I don't use private window? It worked only once and is not able to connect to their servers.
Edited: in the last 2 years the app works flawlessly and I changed the rating to 5 stars.

Updated review from 3 stars to 5 stars:

They reworked the login system for this addon and now it stays logged in. With the previous login system you'd have to relogin like once a week and you couldn't save your login credentials either.

With that being fixed, I have no real complaints about this addon. Sometimes you get slowdowns but that has been the case with every VPN using any type of client I have tried. Addon or dedicated desktop app. Slowdowns happen.