Hello,
When you open up Form Mule, from the dropdown menu go to step1. "Choose source data and set merge type" and check that Form Mule is set to merge on the correct sheet.
If you can not get Form Mule to open to any step without the spinning wheel can you please copy and paste your user key from the Form Mule drop-down onto this thread, we can then check for what errors are occurring.
Thanks!