A PHP error occurred while trying to prepare the AMP response. This may not be caused by the AMP plugin but by some other active plugin or the current theme. You will need to review the error details to determine the source of the error.
It appears the plugin with slug w3-total-cache is responsible; please contact the author.
If you get stuck, you may want to share any details in a new topic on the plugin's support forum.
The exact details of the error are hidden for security reasons. To learn more about this error, enable the WordPress debugging display (by setting both WP_DEBUG and WP_DEBUG_DISPLAY to true), or look into the PHP error log. Learn more about Debugging in WordPress.