Should I continue pursuing this opportunity with Manpower?

I received a call from a verified recruiter at Manpower regarding a position I applied for, which had reopened. They mentioned they would follow up in about three weeks, right before the holiday season, which I understood.

Three weeks later, I got a call back, but I wasn’t able to answer since I was at my current job and couldn’t step away. I returned the call shortly after, but a different recruiter answered. They assured me that my original recruiter would call me back within 20-30 minutes, which sounded fine.

A week went by without any follow-up, so I called to check in. I was told my recruiter would get back to me that day because it was busy. After about four days of waiting, I called again and was informed that they didn’t know why I hadn’t received a call and that they would escalate my case to a supervisor, promising a call back within the hour.

It’s been about two weeks since then with no responses. I’ve attempted to return the call several times, but I haven’t been able to reach anyone and have left voicemails without success. Am I possibly blacklisted from this opportunity? Should I keep trying to follow up?