Import Failed - ClickDimensions Import to Marketing List is resulting in an error but I don't know why

Hi there,

I'm trying to migrate from Mailchimp to Clickdimensions, and in the first instance recreating lists as marketing lists in the system.

I've been able to import some lists fine, but using the exact same upload template am getting an error for others, with no explanation in the import log. Is there a cap on the number of records that can be imported in a single instance? I'm currently working with a list of 17,000 and a list of 70,000.

If not this then what else could have gone wrong - I am solely populating the first name, last name and email (see attached)

Thanks for your help,

Chris