UpPrev box design customizing impossible

Hi Team,

I’ve been trying to customize UpPrev box design using some css but one parameter seems impossible to modify : border-top of the box.
Reading html code reveals a hard code in head section :

<style type=”text/css”>
#upprev_box{bottom:5px;width:360px;left:5px;display:none;display:none;}
#upprev_box {border-top: 2px solid </style>

With it, custom css in UpPrev settings or even using custom css plugin can’t write over it and border-top remains in black colour.

Is there a way to fix it ?

Here is a link to a page : http://reseau-chretien-gironde.fr/eglises-et-associations/associations/eden-kfe-bordeaux/

Many thanks, regards,
Theophil

https://wordpress.org/plugins/upprev/