Order export doesn´t create csv, but opens new page.

-- HikaShop version -- : 2.6.4
-- Joomla version -- : 3.6.4
-- PHP version -- : 7.0.2

HI,
when I try to export orders, it doesn´t generate csv, but opens new page with hikashop menu (not a standard page, but only links with broken diacritics). It used to work normally. We used our customised php for order export view, but even If i delete the customisation and use original version, there is no difference - still no export. Export of products works normally.
I have found advice in this forum to increase memory limit in php.ini. I did - from 128 MB to 256 MB. It didn´t help.
I have also tried to export only one order, but with the same result.
Could you, please, check what coudl be the reason? I have sent admin login details via contact form.
Thank you very much in advance for your help!
Jarka

SOLVED