It’s a known limitation of ChromelPass, but there’s a simple workaround.
7.2 Auto detection of input fields
The detection does only detect fields which are visible when this function is called.
It is only one time called automatically: After loading of the page finished.
For example an overlay for signin or signup could possibly not auto detected by chromeIPass because either the input fields are created just-in-time or they are hidden to the user while auto detection is running.
When it did not detect any username + password field combination you can click on the browser icon of chromeIPass and press the button “Redetect credential fields”.
You can also focus the visible username field or password field and press Ctrl+Shift+U. This will start a redetection for the focused field, too.