Unable to "Let them in" to a chat.

I have a friend on keybase, and we follow each other.
At some point he rekeyed his account, and since then I have been unable to have chats with him.
I have been able to create a group, and in the group we are able to send messages to each other, but the 1-1 messaging system does not work.

When I open a 1-1 chat, I see the following message, however clicking the "Let them in" button seems to perform no action.

I'm currently trying this from the Windows client, running on Windows 10, but I've also seen this happen on the Linux client, and the ios client.

I'm not sure what other information I can send you to help debug this, but it's been an issue for months now, and I'm hoping I can provide some information that can result in a fix.

Start by reproducing the failed “Let them in” action in the 1-1 chat on the Windows, Linux, and iOS clients, checking whether the rekeyed friend is admitted. Done means the button performs an observable action and the two users can exchange direct messages again.

Written by the indexing model from the issue text.