Microsoft Teams integration -> execution expired

Summary

Cannot send notifications to Microsoft teams through gitlab-ee. Works with curl on console same server. Works like a charm with slack

Steps to reproduce

Example Project

What is the current bug behavior?

in application.log i can find those entries:

2020-10-15T11:28:28.990Z: MicrosoftTeams::Notifier: Error while connecting to https://outlook.office.com/webhook/9656ab2b-5b7a-......0341@910e09c8-693e-47a.......f51/IncomingWebhook/b18a9.....098beb8/a20e6d1e-1f5504dd: execution expired

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Debian 10
Proxy:		no
Current User:	git
Using RVM:	no
Ruby Version:	2.6.6p146
Gem Version:	2.7.10
Bundler Version:1.17.3
Rake Version:	12.3.3
Redis Version:	5.0.9
Git Version:	2.28.0
Sidekiq Version:5.2.9
Go Version:	unknown

GitLab information
Version:	13.4.3-ee
Revision:	fd96f779e9d
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	11.9
URL:		[ HIDE ]
HTTP Clone URL:	[ HIDE ]
SSH Clone URL:	[ HIDE ]
Elasticsearch:	yes
Geo:		no
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: 

GitLab Shell
Version:	13.7.0
Repository storage paths:
- default: 	/var/opt/gitlab/git-data/repositories
GitLab Shell path:		/opt/gitlab/embedded/service/gitlab-shell
Git:		/opt/gitlab/embedded/bin/git