rollbar-gem: undefined method `configure' for Rollbar:Module (NoMethodError)

I upgraed Rollbar from 1.5.3 to 2.6.1 and I get the error from issue’s title.

I tried to recreate Rollbar configuration by running:

rails generate rollbar POST_SERVER_ITEM_ACCESS_TOKEN

but the problem remains the same.

What can be wrong?

About this issue

@KamilLelonek change that require 'rollbar/rails' with require 'rollbar'.

Tell me if that works.

Thanks.