Captcha on custom file

Hello,
my website is now ready, I tested it on my web space and everything works fine, except the mail () function, but this is due to my operator.
So I use google smtp for my contact page and it works.
In order to avoid robots, I would like to protect this contact page with a captcha. I have read the Phpmaker help and the phpcaptcha.php but I can’t find anything useful on the forum.
When analyzing the register.php file, I found the following lines:

<? php echo Captcha () -> getHtml (); ?> and <? php echo Captcha () -> getScript ()?> but when I use them for my contact page, I get the following error :

Notice: Undefined property: PHPMaker2020 \ xxxx \ Contact :: $ OffsetColumnClass in D: \ Software \ wamp \ www \ xxxx \ classes \ PhpCaptcha.php on line 132.

Can you help me to use the captcha on my contact page ?

The getHtml() generates HTML to be used in a form, for example, Edit page. In your custom file, since it is not a form, there is no such property as OffsetColumnClass. But you can refer to the source code of getHtml() and put the HTML directly in your custom file.

Unable to use this internal captcha.
I use now Google recaptcha.

Please post your code in that Custom File for more discussion.

I have activated Captcha from the Extensions
and on the custom file I put the following code

<div class="row gx-0 mb-2">
       <?php Captcha()->show(); ?>
</div>

it display an un-readable text