Can't register gitlab runner

Hello,
i am not able to register my gitlab runner. i allways get an error message when i do so.

ERROR: Registering runner… failed runner=h_ysrLEv status=405 Method Not Allowed
PANIC: Failed to register this runner. Perhaps you are having network problems

i use the parameters gitlab suggest me
Specify the following URL during runner setup: http://213.209.124.64/ci
Use the following registration token during setup: h_ysrLEv96KsTPsZWxfm

is there anybody who can help me?

best regards knut

i use GitLab Community Edition 8.12.1 ca3c6a4 and runner version is
sudo gitlab-runner --version
Version: 11.0.2
Git revision: 1db57d4a
Git branch: 11-0-stable
GO version: go1.8.7
Built: 2018-07-16T21:46:29+00:00
OS/Arch: linux/amd64

docker version is
sudo docker version
Client:
Version: 18.06.0-ce
API version: 1.38
Go version: go1.10.3
Git commit: 0ffa825
Built: Wed Jul 18 19:11:02 2018
OS/Arch: linux/amd64
Experimental: false

Server:
Engine:
Version: 18.06.0-ce
API version: 1.38 (minimum version 1.12)
Go version: go1.10.3
Git commit: 0ffa825
Built: Wed Jul 18 19:09:05 2018
OS/Arch: linux/amd64
Experimental: false