If you get a notification that one of the Instagram connections on your Connected Social Accounts page has expired, you'll need to click the refresh arrow icon shown by Instagram (or add the appropriate account in some cases), as shown here:
But if you find that clicking the 'refresh' icon merely refreshes the page and does not fix the issue, it's likely because your browser is logged into a different Instagram account. Juicer will refresh whichever Instagram account your device is currently logged into (if you are logged into any).
On your Connected Social Accounts page, you should see listed in red text the specific Instagram connection that has expired. Go to instagram.com and log into that Instagram account. Then, return to your Connected Social Accounts page at Juicer and click the refresh icon again. This should refresh the specific, expired connection, and stop the notifications from appearing.