IIS https requests freeze issue


I have two PHP websites on IIS both using Let’s Encrypt certificates provided be Certify the Web. One of them is running perfectly with no issue. The other one has some problems.
I will try to explain my problem for you as simple as possible:

1- without any clear reason or any specific time IIS requests for that particular website freezes and the website keeps loading forever.
2- sometimes some requests freeze sometime all of them (for that particular website only)
3- only particular website requests freeze, while the other site are running fine.
4- both websites are PHP & js website .
5- restarting the website itself or the application pool is not solving the problem. I have to restart the whole IIS server.
6- nothing shows up in the logs (as per our experience)
7- One time I reinstalled the website without SSL certificate, and the problem disappeared. As soon as I installed the SSL, it starts freezing again.
9- The website that has the problem has more traffic.

I did a lot of diagnosing and trouble shouting and googling but no luck with it. Finally I am suspecting in two things described below, but I am not sure about them and I don’t know how to solve them either.

1- I think there is some buffer size error in HTTPS requests by IIS where when it reach some amount the IIS failed so serve the content. I am not sure there is special HTTPS buffer but when I use HTTP it works fine.

2- I read on the website about Invalid Private Key Permissions.
the description looks like it is talking about my issue but I am not sure, because as I said the other website is running fine.

for both two mentioned point above I don’t know how to make sure if they are the reason and I don’t know how to solve them.

Please I need your help.


Hi Hanood,

Certify The Web just fetches and installs certificates for you, it doesn’t modify other configuration and as such doesn’t affect the normal operation of your websites.

As general advice I would:

Keep in mind that IIS itself is used by millions of sites with https, many of which use php. It may have bugs but they are not likely to be ones you will encounter regularly on a patched and updated system unless they are caused by custom code.


Thanks for your replay, I think it is directly to the point.
I would like to update you that yesterday it happens again, I noticed that php only is not being served by IIS while html is served fine.
I will go through the points you mentioned and check them one by one.