Hi,
I'm surprised this tool would flag the contact pages.
If you look at the HTML of the contact us buttons, you can see this:
i.imgur.com/XMFlbfe.png
So HikaShop asks search engines to not follow/index the contact buttons.
And thus the fact that different URLs lead to the same contact form page is irrelevant.
Now, what you can do is add the code:
<?php
$doc = JFactory::getDocument();
$doc->addHeadLink(hikashop_cleanURL(hikashop_completeLink('product&task=contact'.$this->url_itemid)), 'canonical');
?>
at the beginning of the view file product / contact in the menu Display>Views.
That way, even if ahrefs ignores the nofollow/noindex on the buttons, it won't complain about the contact form pages.
But it won't change anything for your SEO.