Changing from HTTP to HTTPS results in ERR_CONNECTION_REFUSED for both Mattermost & GitLab

Hi @revxx14,

Have you tried setting all the following in your gitlab.rb? You'll need another SSL certificate just for Mattermost.

mattermost_external_url 'https://mattermost.gitlab.example'
mattermost_nginx['redirect_http_to_https'] = true
mattermost_nginx['ssl_certificate'] = "/etc/gitlab/ssl/mattermost-nginx.crt"
mattermost_nginx['ssl_certificate_key'] = "/etc/gitlab/ssl/mattermost-nginx.key"
mattermost['service_use_ssl'] = true

This is documented here under the section "Running GitLab Mattermost with HTTPS". Let me know if that helps