Do you use an Ad Blocker on your Chrome browser, if synced to mobile Chrome browser?
If you used the Google app on mobile, might want to check if your Chrome settings sync to it if you have Chrome synced on PC/Mac, pending you use an Ad Blocker of course.
Maybe copy/paste to Incognito.
I use neither on mobile, so I can only provide advice.
I actually tried at least 10 times before I could get registered. The message kept saying that my answer for the captcha verify was wrong! They were not! Finally I received notification, but I have not received the bonus yet.