my ipad and iphone doesn't sync google calendar when my mac does

Hi,

since december or so I have been having trouble with my iCalendar. I sync several calendars, one of them is google calendar. This calendar is not visible on my iPad and my iPhone, but it is visible on my Mac. I checked several times if it is marked on my iPhone and my iPad and it is. Still, it doesn't download and I don't see this calendar...

Can anyone help, please?

Thanks