Try the following solutions to get rid of the error "The operation can't be completed because some items had to be skipped" and empty the Trash on Mac:
If you're certain the files you want to empty from Trash on Mac are unlocked, the next step is to ensure your account has read and write access to the files. Right-click the file that you're unable to delete, select "Get Info," then check if your account is designated as Read & Write. If not, click the yellow lock and enter your password, then change the settings.
If that doesn't work, you can force empty the Trash on Mac using Terminal. Open Terminal, type rm -rf followed by a space, then drag and drop files in your Trash can to Terminal to get their paths. Lastly, press the Enter key.
rm -rf file_path
This command will force remove all the files you dragged to Terminal, including the read-only files.