Photostream syncs from iPad to iPhone but not vice versa

Hi -- I just bought a new iPad Air and photos from my Photostream are not showing up in the Photos app. However, I took a test photo on my iPad and it did sync to my Photostream (I was able to view it on my iPhone as well as MacBook Pro). It's just that no other Photostream photos show up on my iPad.

I have tried the troubleshooting steps described here, to no avail: Get help using My Photo Stream - Apple Support.

I have been reading through the discussion forum for similar problems and the solution proposed always seems to be the above steps -- but it doesn't work!

I am using:

iPad Air iOS v. 8.4.1

iPhone 4 (yes, it's old!) iOS v. 7.1.2

MacBook Pro (late 2011) OS X Yosemite cv. 10.10.5

Thanks much!