Troubleshoot: Disable other extensions temporarily to isolate conflicts, and consult the plugin’s documentation or support forum for fixes.
If you downloaded the .rbz file manually via Option 2 or 3, follow these steps to install it into SketchUp 2021: Launch . Download Plugin 1001bit Pro For Sketchup 2021
If by "create piece" you mean making a model using the 1001bit Pro plugin: Download Plugin 1001bit Pro For Sketchup 2021