publish to web won't refresh

For a newly made report I used the "publish to web" function.

The first days it seemed to work well, but now the report won't refresh, so the 2-hourly update wont show in the webpage.

I know there can be a one hour delay, but even than there is no refresh.

Only when I refresh the html page (F5) the reports also update.

For example:

The report on the html page has the last refresh date/time:

The powerBI report itself has been refreshed at 16.03hrs

And at this moment (17.30hrs) the report still hasn't been refreshed.

There haven't been any changes on the website-side. I tried to republish (to web) the reports, used the newly generated iframe code, but still nothing.

Any ideas?