Re-binding your account to Amazon's MWS should solve this problem.
Click your name in the upper right hand corner of InventoryLab and select My Account from the drop down menu
Click Amazon MWS ID from the menu on the left
Click the Bind Automatically button
You will then be taken through a short binding process with your Seller Central account which, at the end, will put you back into InventoryLab.
Please allow 24 hours for any missing data to sync to your account. You should be able to research and list products in about 15 minutes.