"Unable to decrypt" – Cross-signing not working properly

Hi there,

a couple of weeks ago, the Riot App on my iPad stopped working properly. All messages in all chats cannot be decrypted anymore, even older ones. When I click "Re-request encryption keys", a popup tells me to "launch Riot on another device that can decrypt the message". When I do launch Riot Web or Riot on my iPhone however, nothing happens.


When I go to the security settings, click "Complete security" in the cross-signing section and confirm the matching emojis, the iPad App tells me that the process was successful, whereas Riot Web tells me that the verification has been cancelled by the other end.

I already updated all the apps involved, including my synapse instance, but that didn't do the trick.

What should I do to fix this?