3.1.5 -> 4.0 -> 4.1 (as suggested in the upgrade docs).
However, i built a fresh 4.1 machine (on Ubuntu 18.04) and still see the same issue as soon as i switch to email and activate (per the FAQ). Luckily, i tried it in another browser while keeping the current session active so, could revert back when i encountered the same issue.
Please let me know if you need any logs/screenshots.