This question came up yesterday, so I thought I'd make a blog post for any weary souls searching the interwebs for a similar answer... what happens if you try to make a Curtainwall (or storefront) and Revit tells you that there are no Mullion families loaded into your project? Where do you find new mullions??
I guess first of all, let's look at why this might happen; in the case of yesterday's example, someone had previously purged the project, and Revit removed all of the curtainwall types, except one (it needs to retain one) but the default one that it kept didn't have any mullions assigned to it, which meant that when Revit got to mullion families in it's purging effort it decided that no mullion families were being used in the project and it nuked them all out. So when the user went to make a new storefront, and it had no mullions, and he attempted to use the mullion tool, he got the error below:
So the user went to the profile folder, found what appeared to me a mullion profile and attempted to load it in, but got this error:
The problem is that although you can associate a profile with a mullion to change it's shape, you first have to have a mullion already in your project to associate it with. In order to do this you need to re-make one of the default built-in mullions that previously got purged, which you don't actually load in; since mullions are technically a system family (live inside of Revit) it means finding the system family type in your browser, right clicking it and creating a new mullion type:
Now you can associate the profile (if desired) with the new rectangular mullion family to alter it's shape, or in this case the user just adjusted the parameters of the new rectangular mullion to make it work for his storefront type and didn't use the profile after all. Hope that helps someone out there. Have you ever ran into this or a similar error? Let us know in the comment section below, thanks!