Reverse cache not working on start pages

[Dingo]

A small update to my problem:

I started Wireshark and saw that there was no any requests going to my
server as long as I used the cache. The problem seems to be in the cached
content. I changed:

proxy_cache_valid 200 1d;
to
proxy_cache_valid 200 1m;

But I don't seem to get any updates to the cache. No traffic between my
Nginx and IIS, everything is still fetched from the cache.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,276670,276671#msg-276671