Images will not display when accessing them at AWS and with legacy ASP

I am new to AWS. I have done a great deal of background reading/research which always helps when you are trying to resolve a problem.
That being said, I have a problem which I do not understand.
We have an ASP legacy system which will remain in ASP indefinitely.
We have stored pdfs with images – S3 in the AWS cloud.
The images and pdfs are “public”.
Part of the URL is dynamically constructed each time based on the “user” that logins (tagged onto the AWS info) We have a newer system – codeigniter/php –  which will display the pdfs and image just fine with the dynamically created URL.
But will not do so in our ASP legacy system.
I understand that by the simple use of a URL, I should be able to access the pdf etc., and particularly since the pdfs and images are “public”.
I develop using localhost, (PHP-Wampserver) but can also develop ASP.
SO my question is two fold.
Do we need to install a something on our ASP server to enable us to view the images as well??  
And what SDK must I install on my localhost (I am thinking the JavaScript and PHP)
I thought maybe it might be a security/permission issue with the ASP server accessing the cloud but that doesn’t make sense because on the ASP side, it will display the pdf but not the image.
This is becoming urgent and any help/advice/pointers would really be appreciated. Thank you.