I just had to do this 10 mins ago.
There are number of things you can try first before resorting to a full Database reset.
While in the Smart Content Pane, look for the small Striped box top right of the Pane….clicking on that box gives you some options. You want to open the Content DB Maintenence window.
Try 3 first and see if that fixes it.
or lastly 5 which what I ended up doing.
Click thumbnail to see full-size image