it sounds like the dealer didn't inform you that you needed to "season" the canvas ends before going camping.
there also should be a sheet from the canvas manufacturer, in your owner's manual paperwork, recommending you do this.
you're supposed to completely wet down the canvas and allow to dry, BEFORE you go out camping. this allows the threads to swell and fill the seam holes.
there's no need to "waterproof" modern vinyl/canvas.
secondly, are you sure it's not a result of condensation, since you mentioned that it was on the inside of the canvas.
if you don't use Popup Gizmos and don't allow for air movement, you'll probably get condensation.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC