No driver IC on net in Hyperlynx problem
Hyperlynx defaults the model on a bidirectional pin to input and this is very probably the issue you are having.

Selecting 'models' will allow you to select the driver rather than the receiver.

Having selected the net, go to 'Models' -> Assign models / values by net.

Of course, you will need a model at each end of the net, as noted in a comment.

This will bring up a dialogue


Select each end of the link and ensure one of them is set to be a driver. I have not uploaded the next screenshot as my connection appears to be poor, but all you do is select the 'Output' radio button and you are set to go.