systemctl status peertube shows the following error.

Error: ENOENT: no such file or directory, open ‘/var/www/peertube/storage/tmp/plugins-global.css’

Looks like an error because the global.css file is not there. You can temporarily fix the issue by creating the file.

su peertube
touch /var/www/peertube/storage/tmp/plugins-global.css

Probably an issue with a plugin being installed or something of the sort.