Web Service returns blank page

[nidir]

Hello,

I have an app that connects to prestashop webservice. Some of my users have problems trying to connect, because their app returns a blank page.

 

In these cases, when you try access the webservice via url (http://store_url/api) , it will ask you for the webservice key, but after you introduce it, it will ask you again and again for the key. If you press cancel, you get a 503 error with a blank page.

 

If you make a call with curl, you get directly a blank page.

 

Any idea on why the webservice returns 503/blank page? It still happens with error display and debug mode on/off and maintenance mode on/off

 

Regards