@Pon_Athithan It’s likely that you were trying to launch a new multisite install when there was a bug that prevented that from working. I just ran into this today and fixed it.
This was the error:
StandardError: An error has occurred, this and all later migrations canceled:
undefined method `to_sym' for nil:NilClass/var/www/discourse/lib/slug.rb:6:in `for'
I think it’s been broken for the past 22 days, since this pr. If you can make it through our guide, it should work now.