Zscaler asked me for 4 referrals I don't know 4 people from the past job

Hi, I worked as a freelancer in my last job for 2 clients. Zscaler is asking me to provide references to 4 people from my time as a freelancer but I don't know 4 people from back then.

They are telling me they can't proceed with my offer unless I give them 4 names.

What do I do?