Universal Channel limitations
Because there are a lot of channels and not a lot of me, API.chat uses Azure Bot Channel as a proxy for most of the channels. I slowly move the most-used channels from Universal to dedicated channels.
Azure Bot Channel has a set of limitations that defines which channel features can and can't be shown. Bot Framework doing its best to mitigate these limitations as well as the API.chat bot engine.
Bot Channel is free for Standard Channels like Microsoft first-party services (such as Skype, Cortana, and Microsoft Teams) and services with publicly available Bot APIs (such as Facebook and Slack). For Web Chat (Premium channel) - It free plan is limited to 10000 messages/month.
Before connecting a Bot Channel refer to the manual on how to create API.chat Universal Channel first.