<![CDATA[<b>]]>**%1$s<![CDATA[</b>]]>**'s app is using an incompatible protocol. They need to update their app before you can call them.
Error when your chat partner's app is incompatible in terms of Telegram calls. Can't be reproduced in official clients.
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L'application de **%1$s**utilise un protocole incompatible. Son application doit être mise à jour pour que vous puissiez l'appeler.
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Corentin,
Aug 3, 2018 at 17:19