A campaign will not launch while Review still has a blocking row. Each block has a Fix link. Common causes are no sender, no primary list, InMail or Find email still on the graph, or Account Protection preflight.
Read Review, then Fix
Launch stays off until every blocking row is gone.
Open the campaign and select the Review tab.
Read each blocking line. Warnings do not stop launch. Blocks do.
Select Fix on the row. It jumps to Sequence or Settings.
Add a sender if Review says to add at least one sender in Settings.
Select a primary list if Review says to select a primary list in Settings.
Remove InMail or Find email, or switch InMail to Message. Those steps cannot launch.
If a sender fails Account Protection preflight, Fix that sender (seat, kill switch, status, safety) and return to Review.
InMail Review copy is "InMail sending is not available yet. Remove this step or switch to Message to launch." Find email copy is "Find email is not available yet. Remove this step to launch."
Enroll at least one contact before launching. The Conditions tab is Coming soon and is not the place to fix a fork. Use If accepted or If replied on Invitation or Message.