I tried to view the sync settings in Customer Insight Sync in the Settings area. It ran for hours trying to load, and never did. Today, if I visit this setting, I see an error "Error loading control". If I click that message, here are the contents of the error:

Error occured during initialization of control: MscrmControls.CustomerInsightSyncControl.CustomerInsightSyncControl;Message: Object doesn't support this action

TypeError: Object doesn't support this action at eval code (eval code:1:1) at CustomControlHostRoot.prototype._initializeControl (https://wittemannmvp.crm.dynamics.com/uclient/scripts/0.js?v=1.2.24-180302-013059:468:16397) at Anonymous function (https://wittemannmvp.crm.dynamics.com/uclient/scripts/0.js?v=1.2.24-180302-013059:468:5864) at r (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:62238) at e.prototype._settlePromiseFromHandler (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:35876) at e.prototype._settlePromiseAt (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:37234) at e.prototype._settlePromises (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:39097) at n.prototype._drainQueue (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:2131) at n.prototype._drainQueues (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:2189) at drainQueues (https://wittemannmvp.crm.dynamics.com/uclient/scripts/preload.js?v=1.2.24-180302-013059:23:889)