As a heads up, a successful GBXML export may still result in a junk HAP import, particularly if you are working with HAP v5.X (pre-v6 does not use the analytical surface method)
I think the energy optimization and analysis tools within Revit and exporting to gbXML is going to be the most effective path
Saving room boundaries to excel is going to require some parsing into a text format (json, xml?) so that it can be interpreted in the future and converting to gbXML will require some effort
If you want to use rooms you will need to be in the file that has the rooms as the tool does not process rooms in links
Is there any possibility that the export filepath UI is being buried in other windows/monitors? I haven’t seen any similar issues in the autodesk revit forum history.