Google captcha V2 callback not triggered after challenge is completed

[navinkumarc]

Hi Team,

We use google captcha V3 for bot detection and when the score is low, we fallback to V2 to challenge the user. 

We have setup both v3 and v2 as per the docs. We use javascript to programmatically execute V3 and V2 using `grecaptcha.execute( )` method. 

The issue here is that, the registered callback for V2 is not getting triggered for some cases due to which the users are stuck in the captcha step. It gets triggered for staging environment but not in production. Need to understand what is missing here. 

TLDR; Registered the callback in `render` method of V2 as per docs. Calling `execute` invokes the challenge but the callback is not triggered post that.