My buds plus case no longer charges wirelessly. I use official Samsung charging pads and the light turns red but it's not charging the case. I can only do so by connecting the case with a wire.
The best advice I can give is to take it to Samsung for warranty repair. They've been great with my previous Galaxy Buds. They replaced them TWICE under warranty. So if they're not wirelessly charging, get it checked with Samsung.
Bare in mind the Buds+ case will slowly charge wirelessly and the Buds are always charging in the case.