Single-board guests cannot properly send slack messages to their Trello board

[Pamela Horne]

I have a Trello workspace that have multiple boards that contain single-board guests.  I have the Slack power-up on their boards.  They went through the steps to activate their Slack (Slack button).  When they grab a Slack message and drag it to an open card, they get the following message: "This conversation is in a channel you don't have access to."  However, they do have access to this channel in Slack.  

What could be causing this message to appear in Trello?

Also the "Authorize to see details..." button does not work.

When I go to their board (as administrator) and pull over a slack message, I do not get this message and the slack message appears in Trello.

Screenshot 1:  Shows what the member getting the error sees.

Screenshot 2:  Shows the Power up being used

[Sal]

Hi @Pamela Horne – It seems you're experiencing some strange issues when attaching conversations to your cards on Trello. And so, would you mind logging a ticket with us through our contact form? We prefer to handle your case through a ticket rather than a community post, as we will have more tools and options to analyze your issue in more depth. Thanks!