The experimental COM/reflection API has been unavailable since the COM cleanup, apparently:

Now is probably a good time to review the design then.
Actually the COM API has been moved to their library:

aka Rubberduck.API.dll/.tlb.
I had to manually browse to the tlb location in the install folder... is something off with the registration?
The issue is with VBE, not with how we register our libraries. VBE has had exhibited strange behavior in how it choose to display libraries in a list and this has been observed even with Microsoft's own libraries such as shell32.dll.
For that reason, I'm inclined to close this as status-bydesign with the suggestion that the workaround is to use the upcoming reference explorer.
Agreed! I get this feeling many will even forget what the VBE's Project References dialog even looks like in a few weeks... I'd suggest we default the RD libraries to the pinned tab.
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Actually the COM API has been moved to their library:
aka
Rubberduck.API.dll/.tlb.