As my colleague initially noted, we unfortunately do not provide support for sites hosted on IIS. While some people have made it work successfully, it is not a drop-in replacement for a LAMP stack.
And going back to your second post, you mentioned the permissions were:
"IUSR (Modify) + IIS_IUSRS (Read & execute)."
This may be dated information now, but in some notes I found from long ago, the permissions should be set as follows:
The folder in which the software is installed must itself be set with full read/write permissions.
The IUSR_machinename** account itself must be granted all permissions to the folder, not partial.
(** where 'machinename' is the actual server name, so if your server is named "test" it would be the IUSR_test account. This is, or at least was, the account used by default on IIIS).
Is that relevant to your server and the version of IIS on it?