"Blocked Plug-In" when opening pdf from Safari

I have installed OSx 10.12.4 on two machines and since then I cannot open any pdf from a link in an email. I get the "Blocked Plug-In" message. I'm using Safari web browser and gmail via the browser.

This just started.  Here is a link to many others with the same problem. "Blocked Plug-In" when opening pdf from Safari |Official Apple Support Communities

I've already contacted apple. I have been on the phone with them for 4  hours.  They say it is an adobe issue.  I tried to call adobe.  They said they do offer phone support for adobe reader.

I can open the pdf files using a different browser, so it is definitely a safari/adobe thing.