shortcode is interrupting page load

No errors in which console?

Did you turn debugging/logging on and check debug.log in /wp-content/?

What have you upgraded or added recently (plugins, themes, WP Core)?

Did you disable all plugins except this one then reenable others one by one until the problem returned? It’s likely a conflict with another plugin – knowing which one would be helpful.

Thanks for the quick reply.
There is nothing printed in the debug.log
The console I was referring to is the Firebug console in Firefox (useful for spotting JQuery errors)
There was a recent server upgrade (our prime suspect) from one AWS instance to another. PHP went from 5.29 Apache 2.0 to 5.3 FastCGI
In the process, WP upgraded to the latest version (4.6.1)
We disabled all plugins except this one with no change to the symptoms.
We upgraded to the latest version of the plugin, too.

Thanks!

Is the issue still present if just the Salesforce plugin is active?

Correct. With all plugins except the SF plugin turned off, the issue is present. When the widget is enabled, it has the same effect (interrupts the load)

It must be something with the theme, but can you suggest a way to print some kind of error?

To test a theme issue, switch to a bundled theme and see if the issue goes away.

Which theme are you using? Could you provide me with a copy to test against?

The thing is, any errors severe enough to halt output should be automatically output to debug.log…

I switched to Twenty Sixteen and had the exact same results (which seems to indicate that it’s not necessarily the theme). Could the server configuration be the issue?
Thanks for your suggestions…it’s a real mystery!

Well the server is the only thing left. I haven’t seen this issue on any of my testing which is on php 5.3+ so I can’t really help without an error message to point to a possible culprit.

Does the plugin use any specific ports to communicate with SF and if it can’t access SF via those ports it dies?
It’s possible that the server config might have blocked certain ports for security reasons.

Only port 443 and only upon submission.

The culprit turned out to be Captcha. Clearly some server config was fighting with Captcha. I turned Captcha off and all works well again. Thanks for your help and clues.

That was going to be my next suggestion. I really do need to implement the new Google Captcha. If only there were more hours in the day…

Hi Nick,
So, we solved our problem by turning of the Captcha feature, but now we have a spam problem. Have you had a chance to look into the Google Captcha option? Another other ideas about spam control?

Additional FYI. We temporarily fixed the problem by manually adding our own Google recaptcha into the salesforce.php file right above the area where the captcha is invoked. We used the BestWebSoft gooogle recaptcha plugin to do the heavy lifting and simply added their shortcode.

2.7.3 (should release this week) will have built in Google Recaptcha support.