Did you have a layer targeted? What mode was the document in. Perhaps you did not have to reset you preferences.
When I did the steps you outline using Windows 10 CC 2017. When I opened Photoshop alter closeing down Photoshop and not saving the 3D postcard. Photoshop opened in the 3d workspace. I created the new default document and the paint bucket tool worked without problem...
What OS and version of Photoshop are you using?
I cannot replicate any bug but I suspect this is not a bug but you are using the wrong tool.
This is the 3D Material Drop Tool It appears in the toolbar when in the default Photoshop 3D workspace
This is the paintbucket tool it appears in the same slot when in the default Essential wokspace
You can customise your toolbar in any workspace by going to Edit - Toolbar
Thank you JJMack and Davescm for the quick response!
I never used the paint bucket tool in 3D mode, but apparently when switching into the 3D workspace it changed the Paint Bucket tool to the 3D one, but when switching back to the default Essentials workspace it remained set to the 3D Paint Bucket and I never noticed that it changed, so you were correct Davescm. Perhaps Adobe will make it so that this doesn't happen in the future. I've seen others run into similar problems like this when switching between workspaces.
Just as an FYI, I included my versions below.
Adobe Photoshop Version: 2017.1.1 20170425.r.252 2017/04/25:23:00:00 CL 1113967 x64
OS: Windows 10 Pro (all updates applied)
I create my own custom workspaces.
Get everything the way you like it and click New Workspace . Then name it. I set up one for photography, one for 3d and one for video. That way I can quickly switch and know the panels and toolbar are set the way I like them, not the way someone else decided to make them.
Whilst you can change the existing spaces, if you reset them they go back to Photoshop's layout. Resetting your own goes back to the way it was when you created it.
Thank you for the tip Dave, I appreciate it!