I have SQL Server Express 2017 running on Windows Server 2016 Standard (default instance, not named). It has remote connections enabled and is listening on port 1433 and has TCP/IP and Named Pipes enabled. I have several Surface Tablets running Windows 10 and Windows 11. These tablets make a VPN connection to the server to connect to SQL Server. All of the tablets, except one of them, can connect to SQL Server. All tablets connect using the server's IP address and with SQL Server Authentication. All tablets are connected to the same WiFi router - both the ones that CAN connect and the one that CANNOT, so I believe router settings are not the problem.
The tablet that fails to connect can ping the server successfully. It cannot, however, telnet to port 1433 on the server - this times out. All other tablets can make the telnet connection. Also, using sqlcmd to connect (sqlcmd -S ip-address -U user-name -P password) works on all tablets except the one. This returns error 53. Checking the SQL Server logs after attempting to connect using sqlcmd shows no errors. So this tablet is definitely not even reaching SQL Server.
I have disabled all Windows Firewall options on the tablet with no change - still cannot telnet or connect via sqlcmd.
I have walked through multiple remote connection troubleshooting guides step by step, but most of them assume that NO remote systems can connect to SQL Server. In this case, it is just one system. So I know that the server is configured properly to allow remote connections. I just cannot determine what is different about this one tablet that is preventing it from making a connection.
What might be preventing this one system from making this connection? Any settings or other options I should be looking at?