Please follow the below solutions, and that should help you in fixing the issue quickly.
Method 1: Firstly, Launch Windows Firewall and check to look if the essential ports for QuickBooks are available or not. These sections for QuickBooks 2015 are 56725, 55367, and 8019. In spite of these being available, you may still require to check out more over updating. In this way, a user can proceed in Windows Firewall to Find blocked ports. This should fix your errors of Windows firewall blocking QuickBooks or QuickBooks Hosting.
Method 2: You can install, download, and run QuickBooks file doctor. It will naturally open the blocked firewall ports. You can also set up Windows Firewall with this tool. This should hopefully fix the matter.