Please follow the below steps to allow SQL express communication in the firewall.
- Open SQL Configuration Manager (You can find such an option from the start button)
- Expand SQL server network configuration and click on Protocol for SQL Server
- Enable TCP/IP.
- Right-click on TCP/IP and go to properties.
- Add port 1433 in all port text boxes.
- Restart the SQL server services.
- Go to windows firewall with advanced security
- Click on the inbound rule > New Rule > Port > TCP > Specific port (Add port 1433) > Allow connection > Name of the rule and click on save.
- Click on the outbound rule > New Rule > Port > TCP > Specific port (Add port 1433) > Allow connection > Name of the rule and click on save.
If you need any help then you can check Server Migration | Server Management | Server Security (activeservers.in)