Hi Partner,
The error dialog means that the RibbonWorkBench tool you are using is latest version(3.1.443.1), The latest version will now perform checks on the solution before it loads it.
“There are no entities in this solution” error means that need you add at least one entity to the solution, can you share which components you have added?
Also, you need notice following other points, otherwise, other errors will appear:
--You don’t have to add any entity metadata or assets or form in the solution except the entity itself only.

--Other errors:

For more details, you can refer following link:
Speed Up Publishing of Solutions – Ribbon Workbench for Dynamics CRM/365 & Power Platform (uservoice.com)