I have a similar problem with NF.
Initially did not recognised my premium account. Deleted and tried to add again. Now is in a continuous loop check (see img). I can login through browser without any issue and download any direct link.
https://postimg.cc/vDNWr6dm
Edit: Solved account verification issue. For me apparently the CAPTCHA plugin decided to not work on Mozilla. Deleted re-installed, solved CAPTCHA manually and account was verified in seconds. Now everything is bck to normal.