Membership 2 Upgrade - Import Not Working

Hi, I'm writing on behalf of my client who has been using Membership for a few months. It looks like there was recently an upgrade to Membership 2, and now I'm not seeing any of the previous data available. When I click on Membership 2, it comes up with an Import screen. I've tried running this a few times now with different settings and it just hangs at 100% saying "Cleaning up..."

Not sure what to do here as her previous members and data seems unavailable? Does this mean her membership setup is not currently working and protecting her paid content? I hope the previous data has not been lost or can be successfully imported. Please advise what we can do to fix the import process.

Thank you,
Rory