I don't know if it's the app, server or protocol problem but the last time I've evaluated Matrix (Sep 19, based on logs) as a possible Telegram/WhatsApp/Skype/D

I don't know if it's the app, server or protocol problem but the last time I've evaluated Matrix (Sep 19, based on logs) as a possible Telegram/WhatsApp/Skype/Discord replacement there were some weird issues with "Unable to decrypt: The sender's device has not sent us the keys for this message" even after both parties verifying the fingerprints. I've used a desktop/Electron Riot client, the other party had used the web version. Restarting the Riot had helped me to see the new messages, but not the old ones (which feels to be a correct behavior in regards to PFS). The actual problem is other party didn't knew I had issues receiving their messages until I've contacted them out-of-band - conversation looked just normal from the other side (except for me writing "test test" and not replying any meaningfully). We ended up with a decision to try Matrix again sometimes later. Like, next year.