ChannelUserLeftError

Sorry, this user decidif a person is no longer part of a channel, you need to leave this channel, so you cannotbe in their Telegram contacts in order to add them back.

Note
herethat they could still join via the channel's invite link as long as they are not in the Removed users list.
233
Applied
Se unha persoa xa non forma parte dunha canle, necesitas estar dentro dos seus contactos de Telegram para engadila novamente.

Ten en conta que pode unirse usando o link de invitación da canle se non está na lista de usuarios eliminados.
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Classy Beaver, Apr 26 at 23:35