Gravity PDF images

Good day,

On my website I am using the plugin gravity PDF, the plugin creates a PDF file with some images.
It happened sometimes that when the plugin created the PDF it could not get the images (logo and other photos) to put on the PDF document.

Ithemes security forbidded the plugin to get those images. To solve the problem I just deactivated the plugin and activated it back.

Do you have any idea? I really do not know how to solve this issue..