Thanks for asking this question. You’re right the instructions here are not very clear. There are certain Revit process that must be stopped before the Revit connector can be installed. You have the RevitAccelerator process open in the background so you need to end that before the connector will install.
Press Control + Alt + Delete simultaneously on your machine and click the “Task Manager” button
Locate the “RevitAccelerator” process in the list of processes, right click it, and then press end task.
You should be able to install the connector after that
RevitAccelerator is a helper process that launches when you first launch Revit per session.
In my experience, you can use Task Manager to end this process safely. It is only there to make subsequent Revit opens quicker. But it does block installing Speckle from Manager.
Thank you for such quick updates, it works!! Great!