The previous turn I moved a fighter (attached to the HQ in Glasgow) to Inverness (to avoid a possible paradrop raid).
The current turn the fighter is no longer attached by the HQ (in Auto-Assist mode) and can not be reattached;
and yes I unattached a different unit first to clear up a 'space'.
The HQ command range display still shows Inverness to be within range.
So I conclude either the display is incorrect or something to do with the range of attachments is incorrect.

