How do I save an Excel Add-in (XLAM) file?

We had a new(er) version of Excel shoved on us and the result it it doens't do this, so we're sort of in a bad place. How do I save the add-in?   We were probably on an old-ish version because it was stable and upgrades tend to break us - as they have here.  I'm wondering how I save an add-in now.  Right now our workflow is completely broken.

When I go to File--> Save there is no xlam file type available now.  I can still load an old xlam but I can't create a new one.