It sounds like your steerer plug dropped down slightly during transport. This would indicate it wasn't torqued sufficiently. This could be an issue of maintenance or it could have come from the factory like this if it's quite new (no hate on Canyon, mistakes happens with all brands and preassembly).
I asked the brand and model because there are different designs for expander plugs. An expander plug plays the same role as a starnut, but you can't use a starnut in a carbon steerer as it would compromise the steerer. The expander grips the sides of the steerer by expanding uniformly and putting pressure over a larger area than the point connection of a startnut.
The general procedure would be to have the spacers and stem on the steerer (stem not tightened), then the plug is set at the correct height (depends on particular plug/expander but needs to be high enough for the top cap bolt to thread in). The expander is then expanded to the correct torque spec (probably in the range of 5nm, though it's important to look at the specs for your particular type). You want the spacers and stem in place so there is no chance of expanding the steerer. The correct height is important so that it counters the compression of your stem.
Next you would pretension the top cap to remove headset slop. Finally tightening down the stem bolts to the correct torque for a carbon steerer. If available I use friction paste between clamp-on parts and carbon parts (e.g. stem/bar, stem steerer). There is less chance of movement with the lower torque you are allowed to apply to a carbon part (as opposed to alloy).
Since you are travelling I'd recommend popping into a shop that services road bikes. It should be quick and cheap to adjust the expander and torque stuff down to spec (and they'll likely slap some carbon paste on there too).
Unfortunately I wasn't able to find the particular model of expander Canyon uses with a quick google search. There may be info in the manual for you model bike.