Do you mean Photoshop CC?
What country are you trying to download from?
What operating system are you using?
Photoshop version 15 is Photoshop CC 2014 the version I use. The are newer version CC 2015, CC 2015.5 and CC 2017. They have bugs I do not care for. You can install previous version of Photoshop using the Creative Cloud desktop application or down the direct installer and update from the web.
Photoshop version 15 CC 2014 direct downloads links are below. Please follow the download instructions on the download web pages else you will be denied access to the downloads.