I just created a very simple workflow (3 steps). I tried to run it and immediately get an error message " The workflow may contain tools which have changed since it was last saved or some other problems have been detected. Please click here to edit and review the issues before running this workflow." As I’ve just created it I would assume the tools have not changed. When I go back to the workflow there is no indication as to what may be wrong.
Original:
Attempted fix:
Welcome, @lansdowne_bham
Thanks for the screenshots and example!
The correction you made in the screenshots was needed because each input must be included inside of the workflow.
For the example you posted, notice the “red dot” in the Join tool’s box – that was designating a required input (same as a tool form would), so you needed to include either a noodle connection from another tool’s output datasets, or a new “inputs” dataset. You did the latter, and that issue should be fixed now.
As a guess since we can’t see it: Does the Group tool also have an inputs dataset added to the workflow? If not, I would suggest adding that next.
For the remaining problems: what do the automatic checks report?
Find those by
Specific: clicking on the link inside a message like this one
Please click here to edit and review the issues before running this workflow.
Specific + General: reviewing under Best Practices
You can screenshot or copy/paste back any messages in those places that you need help with.
Thanks! 
