Hi,
This is what is called a "blank page". The process stops in the middle because of a fatal error.
It can be due to two things:
- a bug
- a limitation of your hosting
As you're doing an export, it's highly likely to be the second case.
On most websites, if you do the same action again after activating the "error reporting" setting of the Joomla configuration, you'll get an error message at the bottom, telling you what is the problem.
It's highly likely to come from the memory_limit parameter of the php.ini of your web server which is too low for the amount of products to be loaded for the export.
In that case, you would have to contact your hosting company to increase that parameter value, or use a mass action via the menu System>Mass actions with an action "export CSV". With a mass action, you can limit the amount of products to be exported and thus to can get several CSVs of the products with different chuncks so that you get them all.