I am using the VPN and it's staying connected very well, but I find that many sites are so slow that it makes them difficult to use. Other sites just never do load. If I disable the VPN, then they work as normal. Also, if I do a google search I get a message that "abnormal activity" was detected from my computer and I have to fill out a captcha to continue. It's annoying. How do the sites know I am using a VPN and why does it cause these issues?