If your plugin is not being detected by Logic Pro X please try either or all of the following procedures:
Method 1: Run the AU Manager from within Logic Pro X.
Method 2: Go to Macintosh HD/Users/Library/Cashes and move the com.apple.audiounits.cashe file to the trash and empty the trash bin. When you next restart Logic Pro it will do a fresh scan of any installed Audio Units and your plugin should now appear in the Audio Units list in Logic Pro.
Method 3: Go to Macintosh HD/Library/Audio/Plug-ins/Components. If you can see your plugin in the list of Audio Units, select the file and move it to the Desktop. Restart the Mac and start Logic Pro, then shut down Logic Pro and move the Audio Units which were moved to the desktop back into the HD/Library/Audio/Plug-ins/Components folder. Restart Logic Pro and your plugin should now appear in the Audio Units list.