Cannot login on Matomo mobile app

I just created an on-premise Matomo which I can access via the browser but not via the mobile app (iPhone). Is there any specific setting or so which I missed?

Hi,

Do you get any specific error in the app?
Is the HTTPS certificate valid?

Hi, I get a HTTP error, request ‘not found’. I created a new certificate on the web version but did not do anything with the app and the cert.