I am having this same issue. Unable to activate 2FA. Curiously though, I have two sites on the same server. One functions correctly with no issues with 2FA. Here is the time stamp on the Login Security page:
Server Time: 2019-10-25 04:03:46 UTC (2019-10-24 23:03:46 UTC-5)
Browser Time: Fri, 25 Oct 2019 04:03:59 GMT (Fri Oct 25 2019 00:03:59 GMT-0400 (Eastern Daylight Time))
Corrected Time (WF): 2019-10-25 04:03:57 UTC (2019-10-24 23:03:57 UTC-5)
On the site where 2FA is not functioning (remember, same server) here is the time stamp:
Server Time: 2019-10-25 04:02:27 UTC (2019-10-25 00:02:27 America/Toronto)
Browser Time: Fri, 25 Oct 2019 04:02:39 GMT (Fri Oct 25 2019 00:02:39 GMT-0400 (Eastern Daylight Time))
Corrected Time (WF): 2019-10-25 04:02:38 UTC (2019-10-25 00:02:38 America/Toronto)
So I went to settings and rather than set it to Toronto, where I am, I set it to UTC-4 and then the time was correct. However, 2FA STILL would not activate.
And the other curious thing is that 2FA WAS working previously but then all of a sudden, I would try to log in and get a warning that I had to enter my security code when required but that request never showed up.
Something definitely amiss.
Dave