How to use 2 monitors with the Shadow Box ?

Hello, I just bought a Shadow Box to an ex member for use 2 monitors with display ports. I have a 24" Qled samsung and an Asus TUF 32" V32VQ1B.

When I plug in the Asus screen alone, the image is not stable, not sharp. The resolution is directly in 1440p and I can’t change it (monitor or Shadow.

When I plug in both screens, only the Samsung 24" works. The Asus 32" tells me no signal.

Do you think the problem comes from the resolution of the 32" which is too high for the Shadow Box with 2 screens to manage? Or are both screens no longer managed by the Shadow Box?

Thanks for help, I hope there will be:)