This happens when your business country is in the A2P list (US or Canada) and the campaign registration is not finished yet — specifically, no verified messaging service with an attached number exists for your account. Sprwt will not let you compose broadcasts until the A2P 10DLC registration is complete, so it redirects you to Sprwt SMS Campaign Registration. Complete the profile and campaign steps there; once your campaign is verified and at least one number is attached to the messaging service, Compose opens normally.