Matomo statistics are wrong

Hello !
I’ve a problem with Matomo. I’ve installed Matomo on my servers for somes website. Some website has more than 15 000 visits by mouts (according to Google Analytics). Yet, Matomo tell me there are few visits (less than 50).
I’m sure it’s wrong. Monday, on a website, I’ve receive 12 orders when Matomo tell there are only 2 visits…

In the admin dashboard, I’ve no error message.

For install Matomo, we have just to copy and paste the script javascript in the head of the website and to indicate all the domains, haven’t we ?
I’ve seen there is a key API ? What is it for?

Thanks,

Exemples of website :
sortirdanslaube.com (work with matomo and google analytics)
https://bio-thorey.fr/

Accès Matomo :
https://statistiques-media.fr.nf/

Hi,

This is very easily answered:

Your websites have the following URL in the Matomo tracking code:

    var u="https://sc2mediabo.universe.wf/statistiques/matomo/";

But this website has an invalid SSL certificate and therefore can’t be reached by your visitors.

Thanks a lot Lukas !