MarketPress behind Membership broken

Hi, Customer just changed their mind before go-live on domain name and I moved the site from domainA to domainB using a third party backup plugin which works (normally) very well.

Most parameters moved over well on the MarketPressPro and Membership plugin. I changed a couple of things manually and all looked good.

Problem: Members can't checkout, they get prompted to login again when they go to "checkout".

I just don't know what to do about this.

Any suggestions welcomed.

Regards, Callum.