Does your browser have javascript enabled, and cookies? Login via browser, followed by clicking on that should work. In the case of failing, what is the error message?
I couldn’t tell you where the speed issue is. There are a lot of hops on the internet route, and some people in different regions of the world download from different sites. If you use WiFi, then your own WiFi could be an issue. If you have a shared bandwidth connection, e.g., from DSL, then it could be nothing more than competition from other people using the bandwidth. If many people are downloading at the same time from the web server, then it might be competition for available bandwidth from those people as well. Or any mix of the above. You could run a speed test of your connection both during “good” times and “bad” times to see if your connection itself differs: https://www.speedtest.net/
42 bytes is definitely too small. There is some sort of network or server error for this case. I’ve seen some other people mention issues downloading from China, and this may be something specific to your network route, or a stale cache from the NVIDIA servers. Someone from NVIDIA will have to look into this.