QuickBooks Error 3371 occurs due to the damaged QuickBooks system file entitlementDataStore.ecml. The reason behind file damage is the improper shut down of your computer while the QuickBooks software was open, and the file had license properties of your QuickBooks desktop software. To solve error code 3371, you can delete the .ecml files from the windows explorer folders. You should always use the updated windows because the latest software comes with bug fixes. After restarting your computer, you can try to rename the entitlement file (entitlementDataStore.ecml). If unable to fix QuickBooks Error 3371, then consider taking the expert help.