We have integrated invisible recaptcha in one of our websites. Whenever we submit the form it automatically submits.
I read in some google groups that we would get
As of 2019-06-21, it appears that it is sufficient with Google Chrome (v74.0.3729.169) to bring up a new incognito window to force the recaptcha to execute. (I had needed this for our own recaptcha testing, so I'm glad I found it.)
I am still struggling a little bit with this but I found that the following things make invisible recaptcha puzzle more likely to appear:
Log into the recaptcha admin and set it to maximum security
Open your site from an incognito tab.
Sometimes leaving the login page open and trying to login after some time has passed seems to trigger the recaptcha puzzle.
I must admit though that these don't work all of the times and there are times that I really struggle to get it to work.
Update: It seems a bit strange but I have found that the invisible ReCaptcha is more likely to appear when I submit a form using the Enter key instead of pressing a button with the keyboard.