Gitlab Mattermost 502 - Due To Permissions?

I have a relatively fresh install of Omnibus Gitlab Community Edition 11.11.1 and recently activated Mattermost with SSL. Everything was working great until server rebooted. Attempting to reach the mattermost URL results in 502 Bad Gateway from nginx.

See below for error found in /var/log/gitlab/mattermost/

So my question is… what permissions, owner, group should /opt/gitlab/embedded/service/mattermost/ have?

{"level":"error","caller":"web/static.go:27","msg":"Failed to update assets subpath from config","error":"error walking /opt/gitlab/embedded/service/mattermost/client: failed to update /opt/gitlab/embedded/service/mattermost/client/4.aa07f589b8b4b537cd5a.css with subpath /: open /opt/gitlab/embedded/service/mattermost/client/4.aa07f589b8b4b537cd5a.css: permission denied","errorVerbose":"open /opt/gitlab/embedded/service/mattermost/client/4.aa07f589b8b4b537cd5a.css: permission denied\nfailed to update /opt/gitlab/embedded/service/mattermost/client/4.aa07f589b8b4b537cd5a.css with subpath /\ngithub.com/mattermost/mattermost-server/utils.UpdateAssetsSubpath.func1\n\t/go/src/github.com/mattermost/mattermost-server/utils/subpath.go:128\npath/filepath.walk\n\t/usr/local/go/src/path/filepath/path.go:363\npath/filepath.walk\n\t/usr/local/go/src/path/filepath/path.go:387\npath/filepath.Walk\n\t/usr/local/go/src/path/filepath/path.go:409\ngithub.com/mattermost/mattermost-server/utils.UpdateAssetsSubpath\n\t/go/src/github.com/mattermost/mattermost-server/utils/subpath.go:121\ngithub.com/mattermost/mattermost-server/utils.UpdateAssetsSubpathFromConfig\n\t/go/src/github.com/mattermost/mattermost-server/utils/subpath.go:156\ngithub.com/mattermost/mattermost-server/web.(*Web).InitStatic\n\t/go/src/github.com/mattermost/mattermost-server/web/static.go:26\ngithub.com/mattermost/mattermost-server/web.New\n\t/go/src/github.com/mattermost/mattermost-server/web/web.go:39\ngithub.com/mattermost/mattermost-server/cmd/mattermost/commands.runServer\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/commands/server.go:83\ngithub.com/mattermost/mattermost-server/cmd/mattermost/commands.serverCmdF\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/commands/server.go:53\ngithub.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra.(*Command).execute\n\t/go/src/github.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra/command.go:762\ngithub.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra.(*Command).ExecuteC\n\t/go/src/github.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra/command.go:852\ngithub.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra.(*Command).Execute\n\t/go/src/github.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra/command.go:800\ngithub.com/mattermost/mattermost-server/cmd/mattermost/commands.Run\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/commands/root.go:15\nmain.main\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/main.go:30\nruntime.main\n\t/usr/local/go/src/runtime/proc.go:200\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1337\nerror walking /opt/gitlab/embedded/service/mattermost/client\ngithub.com/mattermost/mattermost-server/utils.UpdateAssetsSubpath\n\t/go/src/github.com/mattermost/mattermost-server/utils/subpath.go:136\ngithub.com/mattermost/mattermost-server/utils.UpdateAssetsSubpathFromConfig\n\t/go/src/github.com/mattermost/mattermost-server/utils/subpath.go:156\ngithub.com/mattermost/mattermost-server/web.(*Web).InitStatic\n\t/go/src/github.com/mattermost/mattermost-server/web/static.go:26\ngithub.com/mattermost/mattermost-server/web.New\n\t/go/src/github.com/mattermost/mattermost-server/web/web.go:39\ngithub.com/mattermost/mattermost-server/cmd/mattermost/commands.runServer\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/commands/server.go:83\ngithub.com/mattermost/mattermost-server/cmd/mattermost/commands.serverCmdF\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/commands/server.go:53\ngithub.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra.(*Command).execute\n\t/go/src/github.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra/command.go:762\ngithub.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra.(*Command).ExecuteC\n\t/go/src/github.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra/command.go:852\ngithub.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra.(*Command).Execute\n\t/go/src/github.com/mattermost/mattermost-server/vendor/github.com/spf13/cobra/command.go:800\ngithub.com/mattermost/mattermost-server/cmd/mattermost/commands.Run\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/commands/root.go:15\nmain.main\n\t/go/src/github.com/mattermost/mattermost-server/cmd/mattermost/main.go:30\nruntime.main\n\t/usr/local/go/src/runtime/proc.go:200\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1337"}

Hey @james_gt, welcome to the GitLab Forum!

Have you checked out this documentation piece about GitLab Mattermost? It contains some details which could help you to resolve your issue.