It seems the plugin can’t resolve the variable ${event_definition_title} or the message structure is not correct, I don’t know
Earlier I was using [${stream.title}](${stream_url}) variables and it was working perfectly, getting the stream name + generating a hyperlink in the Telegram message.
I tried to update plugin to 2.3.1 version, which works on Graylog 3.3.0 or later
But, unfortunatelly it still can’t resolve the variable ${event_definition_title}
To use 2.3.7 version I’ll need to update Graylog because it works only on Graylog 4.2.2 or later.
That’s odd, I’m not 100% sure but it may have something to do with the versions used.
Perhaps someone here has resolved this or you could ask the people who created this plugin why it doesn’t work.