Altium: Unconnected port "xxx" at 550,430
Without seeing a schematic, this is difficult to answer.

I would suggest the first thing to check is that the port is ACTUALLY connected.
This warning is in place for people foolish enough to use a grid of 1 unit haphazardly, as you run the risk of ending the track just shy of what you are planning to connect to.

This results in a schematic that looks like it is connected, from a distance, but actually is not.

Otherwise, if you are referring to a port that SHOULD be disconnected, consider using an ERC suppression (the red X) to suppress the warning.
This signifies that you do not care about any warnings/errors from this pin, because you know that it is supposed to be floating.