Can't import customers or stock items from 1.5 to 1.6

[letsplaydarts]

Hi,

I have been happily using Prestashop 1.5.3.0 for the last year.

I really want to upgrade to 1.6 but can't import any of the customer records, sales records or products.
It simply doesn't work!

I have set up a domain name as a test so thankfully it hasn't messed up our original site which is still active.

After installing 1.6, it appears to be working but can't import any of the records from my original site.

Has anyone had similar and did they sort it out please?

Thanks

Paul