Scheduler with webhook

I tried to use webhook for my grav website, but it returns:

{

"error": "Modern scheduler is not enabled"

}

Plugin is correctly installed and activated because I have this message too:

scheduler-webhook le plugin est installé et activé.

Same issue with health.

How to update hours of system scheduler, I have to change "at" parameter for my shared webhosting?

I do no find any config files with that possibility.