Hi Daniel,
In some missions you can moor to a range of bollards to complete a waypoint but in others you need to moor to one particular bollard. Normally, if it is only one bollard, it will be the one nearest the centre of the waypoint circle, but sometimes it can be offset.
The other possibility is that you need to moor to more than one bollard.
When you complete a waypoint and SS08 shows you the next waypoint then you will get some instructions on screen on how to complete the next waypoint, I have found that it is a good idea to read those instructions closely. You can also see most of these instructions in the 'Ships Log'.
My other suggestion would be that you just keep putting ropes out to different bollards until you complete the waypoint.
Regards, Dave