Trying to make a roof section into a solid

I have a section of an irregularly shaped roof that I’d like to trim using solid tools. I’ve drawn lines around the entire shape and made it into a group but it still isn’t a solid. Can anyone telling me what I’m doing wrong. Thanks. Jim

Here’s a link to my Model..

https://we.tl/t-IczOILMxGT

Have you tried using the extension: Sold inspector https://www.youtube.com/watch?v=FbVskOMXWaQ&t=1s

Would help to know what you are working on - but I will assume it is the main roof.

You have a hidden line:

And then you have lots of missing geometry:

No sorry, It’s the rear roof gable. The tag is called ‘roof rear’. I put a copy of that section to the right of the house (as you’re looking from the rear). The triangular shaped object sticking out of the house in the rear is a solid object I’m trying to use to trim the roof gable. A little tricky to explain, sorry..