Problem with External Monitor

HI,

i have a iMac (27-inch, Late 2012) and i am using it with two external monitors. One Monitor: ASUS PB278 works finde in 2560*1440 but the other on eis not recognized correctly. Its an Asus VX24AH https://www.asus.com/de/Monitors/VX24AH/

However is keeps getting recognized as a Monitor: VX24A with 1080p as the top resolution. But it can do also 2560*1440.

I have this display on on newer iMac 5k in the Office and it works fine.

How can I get in to work in the late 2012 model or how can i force my iMac to reload the monitor configuration. The Button to seearch fro the monitor in the system Preferences does not help.

Thanks for your help