Connection lines do not appear when dragging a component

View Configuration > View options > Dimmed Objects

I was playing with the "N" shortcut to "show" and "hide" connections for a particular component. However, one time I must have had the component selected and was moving it when I typed the "N". After that, I could no longer see any connection lines when moving any component. Apparently, if you type "N" while moving a component it changes a mode called the "Net Line Connect Mode" from "Pad to Pad" to "Hidden". The way I finally spotted this was by looking at the "Heads Up Display" as I was moving a component and saw that this mode had been changed to "Hidden".

Tip 1: Try Tapping the N key to Toggle the connection lines while moving a component.

Source:  Connection lines do not appear when dragging a component - Altium Discussion Forums

Thank you Thomas

Tip 2: Tap the [ key to Decrease Mask Level.  Tap the ] key Decrease Mask Level.

Source: Randy Clemmons.

That's it !