PenciDesign Supporter replied
Hi,
The Penci AMP plugin already includes an option that automatically adds the canonical URL to AMP pages, linking them to the original post/page/archive URL to prevent duplicate content issues.
Please go to Appearance → Customize → Penci AMP → Header, and ensure that the option “Disable the canonical tag auto render on AMP pages from Penci AMP plugin” is not checked. Then, check again.
If the issue still persists on your site, please send me your site URL along with a WordPress admin account, and I will help you check it.
Regards,
PenciDesign.