It's the steam server connection that appears to be an issue. I keep getting not responding but you can connect to your server within the actual game using the <ip address>:<port number> but the port number should not be increased by 1.
You can connect directly within Valheim by clicking Start at the Select Character stage, then select the Join Game tab and then select Join IP. Enter <ip address>:<port number> details but do not increase the port number by 1 as you would in Steam and select Connect. You should be able to connect.
Thanks lovestosurf. That seems to have worked as a work around to the issue. Hate having to type the IP everytime i log in and out but at least we can get in now. Thanks!