Tom from Google posted four steps to help those wishing to clean up their AMP errors in the Google Search Console. Those who went AMP already are noticing many errors popping up in the Search Console reports. Especially those who use that WordPress plugin.
Here are the instructions given by Tom to help resolve many of them:
1. Select some articles and run the page through the AMP HTML validator to preview and validate:
a. Open your page in your browser.
b. Add “#development=1” to the URL, for example, https://ampbyexample.com/#development=1.
c. Open the Chrome DevTools console, with mobile device mode emulation enabled, and check for validation errors.
d. Fix your validation errors.
2. Check AMP schema.org Article markup properties in the Structured Data Testing Tool.
a. Ensure that the NewsArticle, Article, or VideoObject Rich Snippet is present.
b. There should be no 'AMP' warnings/errors.
c. Is the logo 'image' attribute within 600x60?
d. Does the logo fit the UI guidelines for logos in the carousel?
3. Check AMP HTML page linking:
a. Is there a rel=amphtml link on the canonical page?
b. Is there a rel=canonical on the amp html page?
c. Is there a rel=amphtml link on the mobile site page, if applicable?
4. Check external resources:
a. URLs of all embedded iframes, videos, custom fonts, pixels, analytics, ads, etc, and similar content need to be fetched via the HTTPS scheme.
b. Don’t use "protocol relative URLs", this might cause problems when the article is loaded via the Google AMP Cache. When a document is served from a cache elsewhere, such as the cdn.ampproject.org, a relative URL will no longer point to your intended canonical. Instead use an absolute URL.
Hopefully those steps will go some way to get your AMP pages up and running! But... if you are still running into issues with any of the steps above while working with the WordPress plugin, be sure to let the team at WP know by filing an issue on their GitHub page here: https://github.com/Automattic/amp-wp/issues
Forum discussion at Google Webmaster Help.