Why can't I access my Ubuntu server from Ubuntu computer? "Unable to access location"

A long time ago I set up an Ubuntu machine to use as a server for my windows and mac os computer which has worked fine with both, in windows I can just browse it from icons and on mac os I type in the IP for the server in the "go" menu.

Getting an ubuntu laptop I thought it would be really easy to access the ubuntu server but everytime I try I get the following message:
"Unable to access location
Failed to mount Windows share: Permission denied"

When going on the "coect to Server" window instead typing the IP of my server doesn't gain my access either.

So what should I do to access the server??

Many thanks

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