Yes, i put bug in title as that is what I believe this is.
I spent a lot of time trying to fix things and I documented it all here. https://forums.xamarin.com/discussion/comment/362759#Comment_362759
Unfortunately, the problem came right back.
Summary:
Using Visual Studio 2017 15.9.6 with a Xamarin.Forms project. I found I am having no issues connecting to my Mac2011, but my Mac2018 is missing simulators of iPhone 7 and above.
I went thru many steps, ultimately I re-installed the Mac fresh and using a test project I connected and found all the simulators were there.
However as soon as I connect while my main project is open, these simulators no longer appear.
Let me take this moment to say, "Thanks to all the Xamarin creators/contributors/supports for this awesome Xamarin magic".
Considering all my steps... these VS tools appear to have a nasty bug.
I've been working for over a year to deliver this app... and now the tooling is blocking me.
Please share any suggestions, but at this point, I think I need paid support services, so I'm not sure which direction to go up the support ladder.
Thanks.