reCAPTCHA couldn't find user-provided function: onloadCallback

I’ve had the same issue and found two solutions:

1. Add the onloadCallback function to window
2. Remove the onload=onloadCallback part from the query string of the script you included in index.html

In your index.html you probably have this:

<script src="https://www.google.com/recaptcha/api.js?onload=onloadCallback&render=explicit" async defer></script>

remove “onload=onLoadCallback”

should look like this:

<script src="https://www.google.com/recaptcha/api.js?&render=explicit" async defer></script>

That worked for me