Warning message and no data showing

Hello, for some reason, I have the message when trying to consult my statistics

Oups… Il y a eu un problème pendant le traitement de la requête. Peut-être que le serveur a eu un souci temporaire, ou peut-être que vous avez demandé un rapport avec trop de données. Veuillez réessayer. Si cette erreur se répète veuillez [contacter votre administrateur Matomo] pour obtenir de l’aide.

I have 100/200 visitors each day. I did create a cron job through URL but it did not fix anything. If I refresh the page, it finally shows. It’s a self installed Matomo.

The site is a WordPress site and I was thinking to use the plugin but I fear it will have an impact on the site.

On which reports does this appear?
Try to check the Matomo logs (.log file on the server)…

Thanks for your suggestion. I found out that the WAF of my webhoster seems to be the reason of slowness (Alwaysdata). I will check that.