hi @Stmorgan
Can you share a bit more about your issue?
Can you show me the error message?
Do you use the label control to display the returned message?
I made a test . There’s no issue on my side.

Set the items property of dropdown1 to:
MicrosoftTeams.GetAllTeams().value
Set the items property of dropdown2 to :
MicrosoftTeams.GetChannelsForGroup(Dropdown1.Selected.id).value
Set the items property of gallery1 to:
MicrosoftTeams.GetMessagesFromChannel(Dropdown1.Selected.id,Dropdown2.Selected.id).value
If you use label control, the app will return error . Because the returned message is a record value.
You can use gallery control to display the message.
regards
eason