If you are using a bridge connection to your database with your online store, you have to retrieve data from web into your local database every time when you are launching Store Manager.
In order to receive data from your online store's database you should click on 'Get Data from Web' option on the top toolbar. In 'Tools' tab select this function from the PHP MySQL Bridge sector.
You can find also this command in Settings -> Preferences -> Database Connection section:
Wait for data to be converted. Depending on your database size it will take from a few seconds to several hours.
However note, that you have to make full backup of your database before continue working. To do this go to Tools -> Database Backup / Restore Wizard.