Hello. I'm doing this project for a masters degree and I'm trying to add 2 mm of outward thickness to my model, but I keep getting the error 'Unable to Thicken the surface'.

I've 'Checked' my model several times and it says that is fine. I've also tried to 'offset' the whole thing but it only works with no more than 4 faces at a time. I'm pretty new in solidworks, can you please help?

I'm sending the file.