Session Sales Navigator and Recruiter import cards are retired. There is no sender checkbox that unlocks them. Pasted Sales Navigator, Recruiter, event, or reactor URLs are not a replacement path.
Use a live import path
Open Contacts → Add contacts for people, or Companies → Add companies for firms.
Choose People database or Company database, or upload a CSV.
Add manually when you have one record, including a LinkedIn URL for identity.
A sender is for outreach, not for unlocking import cards. CRM still shows Coming soon. Settings → Imports keeps historical session jobs readable. Those rows do not offer Retry or Start now. Start a new search from Add contacts or Add companies instead.