When I try to access the 3d warehouse, the window pops up but has 3 gray lines on a white page. The page does not load with the usual search page. There are no buttons I am able to click.
I am able to access the extension warehouse fine, that screens pops up and shows all extensions and search bar, etc.
I just tried 2015 on Win7 with IE 11, and it works. If you are still on Win with 2015, then try clearing IE’s cache, and restart SketchUp, and cookiejar.xml (search forums for clearing this).