This is grayed out because you have a custom background, species, or class applied, which the builder doesn't know how to handle. We'll be quickly releasing a fix for backgrounds (in QA now), which will allow you to get back into the builder and warn you to skip the background slide, but having a custom species or class means the builder doesn't know what to do at all and it causes a bunch of problems. Custom species/classes/backgrounds are coming to the builder soon, but in the meantime you can temporarily remove that custom value and then add it back if you need to level today.
