This article explains how to handle issue when Configuration Wizard is not able to connect to a provided server and database.
SPDocKit won’t connect to a provided server and database
The SQL Server Browser service is not running. When this service is not running you cannot connect to named instances.
The SQL Server Browser service needs to be up and running.
- Open SQL Server Configuration Manager on your SQL server.
- Click on SQL Server Services. Find the SQL Server Browser service, right-click on it and press Start.
- Do not forget to allow inbound traffic on TCP Port 1434.