Can't login: `tsh --proxy=server login CLUSTER`

I always connected to my cluster using:
tsh --proxy=proxy.z login ClusterName && tsh ssh ClusterName

and it worked fine till yesterday but now I get error: unknown method GenerateUserCerts.

It works on the main cluster but not for trusted clusters and I can also create a session on the trusted cluster using the web interface of the main node.

Couldn’t find anything about that error.
Teleport version on Client (Arch Linux)
Teleport v4.1.0 git:v4.1.0-0-g3078799c go1.12.1

on main server (Ubuntu)
Teleport v4.0.2 git:v4.0.2-0-gb7e0e872 go1.12.1

on trusted clusters: one with v4.0.2 (arch linux) and v4.09 (raspbian)

Thanks for help

Updated the main cluster to 4.1. Now it works