I was having trouble developing a new module because it wouldn’t appear in the module browser.
I discovered the reason was that I had a whitelist in my settings file for the plugin, and because it’s a whitelist, the new module wasn’t on it. But removing the whitelist didn’t help, because Rack kept putting it back in, presumably from my subscription.
As far as I can see, you can’t clear the whitelist from the module pages in the library. Even if you click Add All to have all the plugins, you still have a whitelist.
I had to go to the plugins page in the library and I did remove all, add all there and that seems to have sorted it.