Thank you for the details @ryan.lenihan
This problem has been logged to our team for investigation.
There is a subfolder called "SDA" (by default install it is here: C:\Program Files\Autodesk\Revit 2021\SDA
If you have other versions of Revit installed already, Does this help to get the Macro IDE to work for Revit 2021.
- Exit all versions of Revit.
- Install Revit 2021.1.1.3
- Ensure SDA Process is stopped/Kill process if running.
- Backup Revit 2021\SDA Folder
- Delete Revit 2021\SDA Folder
- Copy C:\Program Files\Autodesk\Revit 2019\SDA to C:\Program Files\Autodesk\Revit 2021\SDA
- Launch Revit 2021.1.1.3 to test.
This also works with Revit 2020\SDA and Revit 2022\SDA
Please hit the Accept as Solution button if this helps to solve the issue.