[Anglais uniquement] - I recently had a problem with both devel and devel themer: neither were printing any messages to the page. When I called dpm() my debugging messages didn't show up, and when I enabled the devel themer module the "Themer info" popup wasn't appearing on any page. This small but incredibly annoying problem drove me crazy, and I couldn't immediately find a solution mentioned in the issue queues or elsewhere online. But I eventually figured out it, and here's how to fix it!