You did not explain how much OBC you had to begin with and had before making changes.
As you may have read from other posts, PCL does restore original OBC balance if possible before refunding a credit card. Also, when you cancelled the $40 excursion, it looks like you did not wait a beat for the OBC balance to be restored, so you were charged.
You explained that you booked a higher cost excursion in Juneau - presumably to replace your original. You didn't say if you canceled the original first. If so, did you wait for the OBC to be restored? If not, you are going to be charged again, but the cancel of the original should restore as OBC since the system will look to restore your original OBC balance before using credit card.