Yosemite Photos iCloud photo sharing not working

So I bit the bullet, drank the kool-aid, and converted my primary iPhoto library to Photos with Yosemite 10.10.3.

Overall, fairly impressed, but the iPhoto Shared library has some issues. I had (have) for shared photo streams from the iPhoto library. Those still show up on all of the subscribers devices (mobile and desktop).

The first time I started Photos after the conversion, I went to the "Shared" tab and saw textual representation of the shared photo streams were there, but after a period of time, disappeared. Now, each time I go to the shared tab, it "Scans for recent shared activity", but always comes back as if nothing is shared. and gives the button to "Start Sharing".

I've tried starting new shared streams, modifying one of the old streams from a different device, but absolutely nothing will show the shared streams, nor cal I share anything new.

I have no intention of using the iCloud Photo Library (too expensive for me and not sure I'm that trusting yet).

Any ideas what I might be doing wrong? Anyone else getting the shared photo streams working in Photos?

Thanks!