I'm able to download the small installer for both the trial and retail version of Sound Forge 16, though the download will fail when downloading either 32bit or 64bit versions. I tried turning off my anti-virus as I know that gets recommended, but it didn't work.
Oddly the 64bit version claims a total size requirement of 841.10MB, but only downloads 188.53MB and promptly errors every time (see attached image). The 32bit version is able to download a little further than the 64bit version at a slower bit-rate, but idles a quarter ways through...
I first experienced this with the trial downloader.... Thinking it was a trial issue I went and purchased the software but am still experience the exact same issue when using the provided installer in my email with my key.