This issue happens when hostname to IP conversion doesn't occur in the Windows OS. Try the following steps:
1. Navigate to the following path in your Windows Explorer: C:\Windows\System32\drivers\etc\hosts
2. Open the file "hosts".
3. At the bottom of the file "hosts" where there are no "#" symbols, type in the hostname & IP pair for your server. There should be a space between "hostname" and the IP address. It should look something like this:
12.34.56.789 hostname.domainname.com
This may help MATLAB locate your server.
4. You can then try calling 'opcua' like this:
client = opcua('12.34.56.789', 63500)
Replacing "12.34.56.789" with your server's IP address.
