First of all, go to services.msc and check that the SQL Server Browser service is enabled and running. If it's disabled, right click it and change Start up type to Automatic. Click Apply then ok, then right click the service in the list and choose Start. 

SQL Server Firewall Rule (applies to the SQL Server PC)

The Tradebox SQL Server instance runs on a specific TCP port, and we need that port to be open in the firewall to allow networked PCs to connect to the SQL Server.

We can obtain the port number by opening Sql Server Configuration Manager (Start > Microsoft SQL Server 2019 > Sql Server Configuration Manager)

Expand “SQL Server Network Configuration” and click on “Protocols for TRADEBOX”. In the right hand pane, double click “TCP/IP”.

Scroll to the bottom and you should see a section called “IPAll”. Make a note of the “TCP” port value – in this case, the value is 50327.

Keep an eye out for TCP Dynamic Ports when you're checking the firewall rule. If the port number shows in the TCP Dynamic Ports section rather than TCP Port as shown above, the port has the potential to change and cause problems with access. If you see this, copy the port number from the dynamic ports field into the TCP Port field and apply the changes.

Open Firewall settings (Start > Control Panel > Windows Defender Firewall) and click “Advanced settings” on the left.

Click on “Inbound Rules” in the top left, and sort the list by the “Local Port” column. You will hopefully have a rule called “TRADEBOX”, with a protocol of “TCP” and the same port number you got from SQL Server Configuration Manager earlier.

If you haven’t got that rule, you’ll have to create it. In the top right of the window, under “Actions > Inbound Rules”, choose “New Rule”.

Choose “Port”

Choose “TCP” and “Specific local ports” – enter the port number from Sql Server Configuration Manager here.

Choose “Allow the connection”.

We should *probably* be a bit more careful, but I always tick all 3 boxes.

The description doesn’t matter, but the name should be something helpful – I usually use TRADEBOX by default.