Hello!
I don't really know whether this is fixable or not, but in any case this may be helpful since people will see this and won't create more support issues regarding this.
From what i've heard, roskomnadzor has started blocking Cloudflare by IPs, and since Pretendo seems to be protected by cloudflare (including the http apis used by wii u and 3ds iirc) there's now no way to access Pretendo from russia without proxying all internet connections from your console through a VPN, which might be very challenging to set up for many (especiall non-tech savvy) people.
The easiest solution would be to create a hotspot on an android phone with the "allow connected devices to use the vpn connection" setting enabled. That seems to bypass the restrictions set by roskomnadzor.
Though if anyone knows an easier method, I'd really like to learn about it.
:(