User verification does not work on Conduit

[timokoesters]

Steps to reproduce

1. register two users on a conduit homeserver
2. start emoji verification between element web and element ios
3. after the verification is done, the shield is still grey

When trying again between element web and another element web, user verification works, so this is a problem with ios. Conduit sometimes sends to-device events multiple times or maybe in a wrong order, maybe that's an issue?

[timokoesters]

Here are some more interesting findings:

first attempt: web-ios - completed verification 2 times initiated by me, nothing changed second attempt: web-web - completed verification 1 time initiated by me, other person got green shield and green shield in left corner of chat (but my profile didn't get green shield and other person seen grey shield) after second attempt other person turned sending messages only to verified sessions and i couldn't decrypt them (all of my sessions are verified using cross-signing) third attempt: web-web - completed verification 1 time initiated by other person, now working just fine, both got green shields on each other

[alexindigo]

Same here, seems to be broken with different clients (Element iOS, Element MacOS, Element X iOS, Fluffy Chat iOS).

[alexindigo]

In the client seeing Verification Request message, with buttons Decline and Accept, clicking any button does nothing.

Also, not seeing anything related in the conduit logs, although I see a lot of WARN conduit: Method not allowed: PUT /_matrix/client/r0/room_keys/keys?version=3253, version number changes time to time.