A new annexe or set of wall awning walls will be manufactured from canvas that has been treated to repel water and inhibit mold.
It is normal to experience initial seepage through the seams. You may like to set up your annexe prior to your first trip and give it a hose down. Allow it to dry then repeat the process. This will allow for the expected slight shrinkage of the fabric around the seams.
No further waterproofing treatment should be applied at this stage.
When the canvas eventually starts to leak, it's time to re-waterproof your canvas with a special solution.