https://bugs.winehq.org/show_bug.cgi?id=42297
--- Comment #2 from proveit@tutamail.com --- Well, that is precisely the bug for me; Wine doesn't automatically install gecko and mono while the prefix is being created. I tested it on a new computer that had never had Wine installed, and Wine immediately prompted me to install Gecko and Mono as soon as a new prefix was created, so the problem isn't universal.
However, I seem to have done something to the computer with the bug that makes Wine NOT prompt me even on a clean prefix, which is the strange part. Since it's a clean prefix, it could not possibly have gecko or mono installed.
It's the exact same version of Wine on both computers: 2.0rc6. Have I simply changed a setting accidentally that blocks the prompt on newly created prefixes?