You need to rollback and install all of the rolls and features required by the website if any are missing.
I have not found any easy way to do this after the install, so it's easiest to rollback and then select everything under .NET and IIS along with every other roll or feature documented in the install guide.
If you look at the "handler mappings" in IIS of the default website prior to the install, you must see all of these:
<Please see attached file for image>

(This is just an example. I don't believe BSI needs classic ASP)
additionally, check the BsiAppPool. This does not get setup correctly in 2016.
The basic settings should look like this:
<Please see attached file for image>

and the advanced settings must enable 32-bit applications like this:
<Please see attached file for image>