I have similar problem recently. I went to the arboretum close to Prague, where they do specialize in growing rhododendrons and have their own sorts, which I have also. I was told, that some plants need a time (you know, as it is in Bible, each thing needs its own time) to start grow and/or blossom. Especially, if the original place, where they grow, was different from where you relocate them.
It seems, this is your case, as you said leaves had normal colour. Be patient. I had to wait three years and this year I have white bush.
Good luck.

Also some of the species rhododendrons can be extremely difficult to flower. We have one we grow purely for its foliage effect - I doubt it will ever flower.

If you have been having to prune it regularly, pruning too late in the summer will also cut off the next year's flower buds.