When I insert a part into an assy and mate it to a surface and then I try to add another mate sw tells me it is over constrained. This happens from time to time.
None of the parts are downloaded. I have designed each part and all edges at 90°. There is no reason for it to be over constrained with one mate.
1) depends on the 2 mates and the geometry mated to them.
2) What do you mean by "None of the parts are downloaded". I do not understand this.
3) Can you share the assembly (pack and go) here? How can I attach a file to a forum post?