Element shows "Decryption key withheld" when it wasn't

[richvdh]

When Element Android (and other clients based on matrix-android-sdk2) gets an m.room_key_request for a key that it doesn't have, it sends an m.room_key.withheld message with a code of m.unavailable (see implementation).

Having received the m.unavailable response, Element-web shows "Decryption key withheld", which is misleading at best.

[robertmx]

Well #23745 was S-Major, as were some of the related bug reports. If the the chat suddenly stops working completely it probably should not be considered a minor inconvenience. I mean the core functionality breaks irrevocably without user interaction and does not recover without "expert" technical assistance.

Therefore I think it is appropriate to upgrade to S-major.

[richvdh]

Therefore I think it is appropriate to upgrade to S-major.

It's just a misleading error message; this issue does not cause "the chat suddenly stops working completely". You may be thinking of some of the other crypto bugs, tracked at element-hq/element-meta#245.