How to use Altium Buses?
I would use Net Labels to connect buses together. Ports are mostly used when connecting nets from different sheets.
As The Photon says, the 8 signals from the left IC must have the same net label as the 8 signals from the right IC.
Your bus connection should look like this:


Buses are used to graphically represent how a group of related
signals, such as a data bus, is connected on a sheet. They are also
used to collect together all the signals belonging to a bus on a sheet
and connecting them to a port to enter or leave a sheet. In this
instance, they must have a net label of this format: D[0..7].
When it comes to buses, the only way to establish connectivity between
a bus and the individual lines within it, is through logical
connectivity between net labels. The use of bus wires and bus taps is
merely a visual aid. Connectivity will be establish regardless of
whether they are present or not.


For more information about buses:

Connectivity and Multi-Sheet Design
Altium Training Video: What is the best way for me to wire up my
schematics?, video #2