Pnp4nagios graphs in distribututed monitoring not shown - strict-origin-when-cross-origin

First step is to check the defined “URL prefix” inside your definition of the distributed sites.
This should a relative prefix like “/worker1/”.
If you have done this you also need a reverse proxy / rewrite configuration inside your system Apache.
It is needed that your Apache knows how to handle the /worker1/ prefix.

This is the link to the manual article.