Red banner & "Accept" button on follower profile.

I started following a colleague on Keybase some time ago. This morning he followed me back. Looking at his profile again shows it with a red banner and another set of buttons underneath:

Pressing the `Accept` button does nothing. What does this mean? How to resolve this? I don't have that with my other colleagues.

FYI: My colleague did inform me he revoked one of his own devices.

Environment:
* MacOS X High Sierra 10.13.1
* Keybase Version 1.0.36-20171122003217+f68b10ef8
* Running Keybase with a non-administrator account.

(BTW, you should update the year in the copyright notice.)

Start by reproducing the red banner and inactive Accept button on the follower profile using the stated macOS and Keybase versions, then trace the profile and follow-state behavior in the client. Clarify what the revoked device changes, and consider the issue done when the behavior is resolved or its meaning is clearly communicated to the user.

Written by the indexing model from the issue text.