Hello,
A member of the brazilian forum replied showing the solution here: https://moodle.org/mod/forum/discuss.php?d=380580#p1534343
The reason of the problem was: Moodle does not accept v3 of the Recaptcha.
So, you need to use v2.
Re: ReCaptcha v3 does not work in Moodle 3.6.1 - ERROR for site owner: key type is invalid
by Dragon DF -
Number of replies: 2
In reply to Dragon DF
Re: ReCaptcha v3 does not work in Moodle 3.6.1 - ERROR for site owner: key type is invalid
by Moses M. Mwebaze -
This saved me the trouble. Thanks
In reply to Dragon DF
Re: ReCaptcha v3 does not work in Moodle 3.6.1 - ERROR for site owner: key type is invalid
by Rachid El Baji -
Thanks for your answer.