Chrome extensions (and/or tampermonkey scripts) not running on certain websites (like gmail) - google-chrome-extension

Question

I have a very simple chrome extension that refuses to run on some sites like https://mail.google.com. It runs fine on other sites which makes me think something is limiting extensions/scripts from running on some sites. The sample case is quite simple and listed below.
With this sample case I see "Hello world" in the developer console when I navigate to https://about.me. I also see the extension in the Developer Console's Execution Context Selector. However, when I navigate to https://mail.google.com I don't see the log entry or the extension in the Execution Context Selector.
I have tried something similar with tampermonkey and am not seeing that script run on gmail either. Thanks!
manifest.json:
{
"manifest_version": 2,
"name": "Gmail extension test",
"version": "0.1.9",
"description": "Try running inside gmail page",
"content_scripts": [{
"all_frames": true,
"js": ["content.js"],
"matches": [
"https://mail.google.com/*",
"https://about.me/*",
"http://*/*",
"https://*/*"
]
}]
}
content.js:
console.warn("Hello world");
Environment:
Chrome 66.0.3359.117
macOS 10.13.3 (17D102)

Answer 1

As #wOxxOm suggested. I tracked down the problem to the fact that my company has a Chrome policy set against running extensions on the google.com domain. I had no warning entries in the Developer Console or the macOS Console, I just tracked down other folks complaining about in an internal forum.
The policy that applies in this case is ExtensionSettings which is set in a OS/device specific way. To help diagnose this restriction, you can view your active polices in Chrome under chrome://policy/. In my case I had something like the following in my chrome://policy:
{
"*": {
...
"runtime_blocked_hosts": [ "*://*.google.com", ....]
},
I'm not aware of a generic workaround for this at the extension level. Instead I had to work with my company IT department to whitelist the extension.