Try the following:

1. Restart your computer
2. Update Primer: Ensure that you have the latest version of Primer installed. You can download the latest version by logging into your online account and selecting “Tools” from the top left dropdown.
3. Verify Installation: Make sure Primer is installed in the correct location. It should be in your Component plugins folder, typically located at /Library/Audio/Plug-Ins/Components or ~/Library/Audio/Plug-Ins/Components
4. Rescan Plugins in Logic: Open Logic Pro and go to Logic Pro -> Preferences -> Plug-in Manager. Click on Full Audio Unit Reset and then Rescan All. This forces Logic to rescan all installed plugins.
5. Create a New Project: Create a new empty project in Logic. Add a new Software Instrument track, and check if Primer appears in the instrument list.