QuickBooks Error H505 usually occurs because the Firewall on your device cannot read QuickBooks and hence blocks the program. Follow the steps below to change the firewall settings and troubleshoot the error: • Step 1: Open the control panel and go to the firewall settings. • Step 2: Click the edit option and select ‘Add exceptions.’ • Step 3: Go through the list of programs and look for QuickBooks. • Step 4: Add QuickBooks to the exception list and then restart your computer. If you notice that QuickBooks Error H505 persists, then you can call the QuickBooks support and consult a certified software expert to implement a more advanced solution to fix the problem. Solved: QuickBooks phone number