As the comments could be removed at some point I'll transform @Bob1's comment into an answer:
This page here essentially explains step-by-step how to solve your problem - they also talk about a Marmot Limelight tent, and also have the issue that one of the transparent 'windows' came loose.
--> MARMOT TENT – REPAIRING POLYURETHANE WINDOWS
To summarize (in case the link gets broken in the future):
- Peel the window off completely.
- Peel off any glue remainders.
- Clean area of old glue residue with some cleaning alcohol (only the seam part, try not to get it on other areas of the tent).
- Apply new proper glue in the place where you cleaned off the old glue . The linked page recommends "Seam Grip" - maybe just ask your local outdoor store, they should be able to help you.
- Glue in the window and put some weights on it so it doesn't move during curing.
- Enjoy newly sealed window!