Change lock screen image by GPO

We need to change the screen lock image and the paper of the computers in my network (about 60 approx) using GPO's, we have created an OU named Pruebas_GPO and in it we have a team and a user named pgpo1.

To make the change we have created 2 Group Directives

screen lock image
 >> Computer Configuration >> Policies >> Administrative Templates >> Control Panel >> Personalization >>
"Apply a specific default lock screen image".
"Avoid changing the image of the lock screen"

In this screen we indicate the route and enable it. The route that we indicate is where the image is hosted and accessible to all users, \\ ServerXX \ Images.

wallpaper
>> User Configuration >> Policies >> Administrative Templates >> Active Desktop >>
"Do not allow changes"
"Desktop wallpaper"

And finally we do a gpupdate / force

The problem that we have is that we do not apply this GPO screen lock image when we log in with the user pgpo1 on the OU computer.
On the other hand, if we apply the carpet change GPO that is configured at the user level.

Server Windows server 2012 R2 Version 6.3 compilation 9600

Windows 10 Version 1803 Compilation SO 17134.556


We have tried to Configure the 2 changes in the same GPO and it does not work, we have also used a PowerShell scritp and change the image, but when applying the directive to avoid the change of image it puts a predefined Windows image.

The images are JPG with 1920 x 1200 pixels.

Could someone tell us where we are failing? Can it be the server version?