For billing, key or custom support, please contact Humble Bundle here.
We are a small team and we have a big audience, so we lean on our community to help out. You guys often know more about current problems and fixes than we do! So for technical support, you'll probably find the answer to your question faster by searching in this forum and asking.
If that doesn't work, contact the dev team here. We will do our best to get back to you (and soon).