Slack Command 404 Error (gitlab.com)

Summary

after creating a custom integration /slashcommand at https://xxxxxxx.slack.com/services/SERVICENAME and a Slack Command at https://gitlab.com/xxxxx/xxxxxservices/slack_slash_commands/edit according the manual i get a 404 when running the command from slack

Steps to reproduce

create the slack command and fill out the url and the token and then run the command on slack

Expected behavior

Actual behavior

got a 404

Relevant logs and/or screenshots

Slack

Gitlab

Chat

Output of checks

This bug happens on GitLab.com

Results of GitLab application Check

Possible fixes