Visualisation Incomplete?

Is there a reason why the visualisation would show all of my devices but only 2 have a link?
In general my zigbee devices work fine, but even after HA has been running for hours the diagram shows no interconnects?

I have added a repeater to try and improve signal for an outdoor sensor hence looking into the visualisation page to see if it worked. However, I have then discovered that only the repeater and a single device show connectivity despite the others all working fine!

N.B. The red sensor on the diagram is effectively unused.