The Sil NET Silicone Seam Sealer is a handy product that lets you seal seams and repair holes in a silicone based fabric. SilNet is the only sealer that will bond to silicone based fabrics.
Gear Aid says:
Seam sealing with Seam Grip SIL is the best way to keep moisture out when using a silnylon (silicone-nylon) tent. Previously known as SilNet, this clear sealant dries to a flexible rubber that works on all silicone treated gear including nylon tarps and ultralight backpacks. One tube can seal up to 24 ft of seams. Fast and easy to use, it’s also handy for pinhole repairs and small tears. When you need to waterproof a silnylon tent only a silicone sealant will work, because silicone will only adhere to silicone. So, treat gear right and seal out the weather with Seam Grip SIL.