Muting Permission Set Groups under the exercise as follows will not let me create a new muting session

Create a muting permission set.

1. From Setup, in Quick Find type Permission Set Groups and then select Permission Set Groups.
2. Click Sales Processing—the permission set group you created in Unit 2.
3. Under Permission Sets click Muting Permission Set in Group.
4. Click New. (This is the issue that I have the "New" is grayed out.  Message says that I cannot have more than one "Muting Session"
5. For label use Contracts Permissions Muted.
6. For API Name, use Contracts_Permissions_Muted.
7. Save the muting permission set.