I don't think Shimmer is not happy. You seem to be taking quite good care of him! Not all betta's make the nests on their own and they only make them if they have good opportunities. I.e. Calm water spot with maybe something like a leaf on the surface which he can build against. Also, you only got smmer recently, didn't you? I had mine for a month before he started making bubblenests and he only does them when there is a leaf flush with the surface or at least breaking the surface