When archiving a Target Activity, '(deactivated)' gets added to the Activity name. ie: AB_Paywall_PriceSensitivity_052019 (deactivated)
At that point, any Analytics Workspaces for that activity will no longer work. Everything turns to 0's. All tables, visualizations and calculated metrics have to be recreated based on the new activity name.
Under the Activities tab, you can see in the status field that the activity has been archived, it shouldn't be necessary to change the activity name also.
Here's a Workspace for an activity recently archived.