Our sunroom is about 20 years old here in Southern Ontario, Canada. It is a modular style 4-season pxl_20210606_135436592.jpgpxl_20210606_135456033.jpgpxl_20210606_135525505.jpgsunroom made up of four-foot panels and is, in total, roughly 20 x 12 with windows along the three sides. The roof panels are about 4" thick and the ceiling has - to my knowledge - never leaked along the seams. (though it had leaked for a short while between where it meets the house)

We recently had the roof shingled over a plywood base, but the issue I am having precedes that.

One of the panels - at the seam - seems to be becoming disconnected from the adjacent panel. It is not leaking, but we are getting what appears to be a brown styrofoam kind of dust coming down from it.

It looks like they should just click together.... but they don't seem to.

Any thoughts on what I could do here, based on a knowledge of what I am working with and how these things fit together?

I assumed the skin on these panels would be aluminum, but one person who came over and tapped on it with his fingernails seems to think that, despite the places where it is corroding a bit, they might actually be plastic.

We were originally thinking to drywall over it, but it doesn't appear that there will be anything to affix strapping to. Even if we could just fasten it back into place that would be okay.

Thank you!