HTTP 500 while trying to open SharePoint Page

Occasionally I had an issue where I was unable to open a SharePoint URL - but only on one server (I run a SharePoint Farm with 2 Application and 2 Web Servers). Every other Web Application on every Server were fine, but this one Web Application on this particular Server could not be opened.

I got an "The website cannot display the page" (HTTP 500)

There were no logs in ULS, no hints in Event Viewer, nothing in Central Administration.

I came across this blog post: Enable Failed Tracing Request Logging

So I first enabled Failed Tracing Request Logging on the particular Web Application as described in the blog post. Then I tried to open the site again which generated an XML file:

Module "SharePoint14Module" could not be found

What did not help me. But googling around, I found this one: Cannot access Central Administration - "Module SharePoint14Module could not be found"

So open Run > type inetsrv > navigate to Config folder > open ApplicationHost.config with a text editor like Notepad or Notepad++.

Search for the <globalModules> tag and the line starting with <add name="SharePoint14Module"...

All the Application Pool names sre mentioned in this line. I compared this line with the data from another SharePoint Server and found a small typo: one of the names was not written with a capital letter:

this one didn't work

fixed.

After changing the one letter to CAPITAL and iisresetting, I was able to access the SharePoint Page.