Bot Framework Skype for Business channel is no longer supported (since July 2019)
I missed this happening at the time, but the Skype for Business channel for the Bot Framework is now showing a message to the effect that support for it ended at the end of June 2019:
This message was added to the page on April 12, 2019.
The Skype for Business channel has always been in Developer Preview since it was made available. It was a good way to expose Bot Framework functionality in Skype for Business. It was a channel that could be used with Skype for Business Online and Hybrid environments only.
It’s a shame, but not a surprise, to see this functionality removed. Microsoft Teams is clearly the preferred solution now, and the announcement that Skype for Business Online will sunset in 2021 removed any need to take this channel forward into production.
If you’re using this channel today, my advice would be to start work to move off it. It’s not clear when the channel will stop working, but when it does, there won’t be any support for getting it working again.