When I check windscribe website, I don't see a free plan, seems all paid now.
However, a decent VPN will always cost some money.

The idea of the user agent I would also check first. I noticed once, when you
use HTTrack without any change to the user agent, it comes with its own one,
which clearly identifies HTTrack tool. Once I hit a website, which explicitly
checked for that and did that kind of "fake banning" thing. A change of the
user agent to a real one solved that issue. 
Could be the same here as Nijaz outlined.