Image set with "$" works offline but not online

Description of the problem:

I have set an image component to dispaly images in this way:
$"istruzioni6_" + expInfo['sessione'] + ".png"

This works in the builder, but when I try the experiment online I get this error:

when setting the image of ImageStim: image_13
when getting the value of resource: istruzioni6_1.png
unknown resource

The strange thing is that I also have a bunch of loop set in the same way (e.g. $"2back_task" + expInfo['sessione'] + expInfo['condizione'] + ".xlsx") and they work fine both online and offline.

Does anyone have a solution to my problem?
Thank you!


The issue seems to be that you need to add the resource in the online tab of Experiment Settings, and nothing specific to the use of the $.