I'd try aquaseal mixed with cotol accelerator. Clean the seams well with rubbing alcohol first to remove any left over adhesive. Then mix the aquaseal and cotol in an approximatly 2:1 ratio. If that seems too thick, slowly add a little bit more cotol until it makes a consistancy about that of maple syrup. Use a little brush or popsicle stick to brush on the mixture to the seam and push the tape back down. If this doesn't work and you're in the Boulder area, bring it by our shop and we might be able to make another reccomendation or help you fix it.
2510 47th St #A1, Boulder