Your CSV import process stops and displays the following error:
Fatal error: Uncaught exception 'PrestaShopException' with message 'Property SpecificPrice->From is not valid'
This error means that a 'from date' of the specific price in your csv file is incorrect.
The format has to be YYYY-MM-DD hh:mm:ss
Modify your csv file and you'll be able to start your import again.