How to determine why Telegram is not available through a proxy on AWS?

Question

Amazon Web Services

I launched an instance in AWS in the eu-central-1b zone with ubuntu 18.
Raised 3proxy, forwarded the port to Security Groups.
Registered in the browser IP and port. I open 2ip.ru - it shows the IP of the instance, i.e. the proxy is working.
However, I try to open telegram.org - it breaks the connection , as with the RKN.
All other sites open without problems.
I do wget telegram.org in the console of the instance - the capital one is downloaded, as it should.
I transferred the instance to us-west-1b - telegram.org opened in the browser and application, but the speed and ping suffer, of course.
Why doesn't it work in the European zone? Any ideas?