1.7 Back office admin page is blank when _PS_MODE_DEV_ is set to false

[prestabee]

Hi, I have just installed prestashop 1.7.6.7 on the latest xampp server which is running PHP 7.2.

My installation was succesful and I had no issues accessing both the front page and back office. However, I started experiencing a problem when trying to acces the back office, it will only show a blank page.

I thought this was due to an error so I decided to switch into developer mode to see if there will be any debug info.
Therefore I modified the defines.inc.php file by changing define('_PS_MODE_DEV_', false) to define('_PS_MODE_DEV_', true)
When I refresh the back office admin login page, it loads without problems and presents me with the login form etc.
If I reset _PS_MODE_DEV_ to its initial value of 'false', the back office immediately goes blank and cannot be loaded again.

Has anyone observed this before? Any help will be appreciated. Thanks.

[hardstonepaul]

Hello yes I work without smarty cache.