Order Files Upload error

When I try to upload a file from frontend with Order Files Upload for Virtuemart i get thsi error: ERROR: Internal Server Error
www.incisoriasacchetti.it/negozio-timbri...-bis-trodat-4913-bis
Before you ask me credentials (I don't like to give them outside my team) I would like to investigate about this issue by myself but I can't understand where I would find uploaded photos.
What's the path?

Hello Davide,

You would see all the photos uploaded in the subdirectories of the below directory:

[ Joomla root ]/vmorder-designNuploads

Danish Iqbal wrote: Hello Davide,

You would see all the photos uploaded in the subdirectories of the below directory:

[ Joomla root ]/vmorder-designNuploads

I've not that folder.
I've removed the plugin and I've re-installed it using your exact procedure but I still have not that folder.
So I've tried to create it manually but that error persist and no file are uploaded.

Also your stylesheet conflicts with T3 framework stylesheets, probably because you use the same names (ex. .product .product-Fields-fields-title-wrapper), so pages are displayed wrong.
LINK 1: www.incisoriasacchetti.it/negozio-timbri...-bis-trodat-4913-bis
LINK 2: www.incisoriasacchetti.it/negozio/targhe...-ottone-bordo-lucido

Images...

Hello Davide,
Please find my comments below:

1 & 2. We don't write CSS for these things in our extension because then it will conflict with the template CSS. That's why your template automatically is applied. Please check template CSS for the following reasons:

1st image: due to box-sizing value of your template
2nd image: due to position absolute and margin in negative value

3) .product .product-Fields-fields-title-wrapper class generated by Virtuemart not by our plugin. Plugin code is inside this class. Template CSS needs to be modified to display the plugins content properly.
4) Seems to be a file permission issue on your server, Please try to install it either on localhost or some other server.

Danish Iqbal wrote: 4) Seems to be a file permission issue on your server, Please try to install it either on localhost or some other server.

I don't have any localhost server for trying but I've tried on demo.joomla.org/ and it seems have a similar issue: no images upploaded, but different error message.