Running uno clean means that the project needs to be rebuilt, and that can take some time. Depending on the hardware specs of your computer and the size/complexity of the project, that time can become quite long (we’ve seen more than 5 minutes build times occasionally).
Without further details, there’s not much else we can suggest.
Kennan – I experienced this same issue. Ultimately, I discovered I had incorrect formatting in my .unoproject file. Unfortunately, I received no errors other than the project hanging in building state. Once I ran uno clean, I discovered the formatting issue and repaired it. I was then able to successfully clean the project and it proceeded to build and operate properly.