Invalid Model

[Vagulus]

My STL, when loaded, is flagged as invalid.

I have printed this before without the embossing

but if I suppress the embossing I get the same rejection result.

Can anyone suggest reasons for rejection.
Thanks.

I have attached the un-embossed STL because the more complicated version is too large to attach. The PDF is of the same device although an earlier iteration. The ZIP is an Inventor IPT which will not load unzipped.