I’ve been using AMP with the official markup for a long time, I’ve never had any problems.
This morning I received an email from google, report the following error:
The mandatory "amphtml engine v0.js script" tag is missing or incorrect.
My AMP pages are no longer valid.
Actually, this tag can not be found in the amp.hbs file
Do you need any updates?
My mistake, this was missing.
<script async src="https://cdn.ampproject.org/v0.js"></script>