P2425, unable to increase brightness

I'm running Windows 11 on an Optiplex 7020 SFF Plus and have 2 P2425 monitors (non HDR). It's a brand new set up. I find the brightness a little dull and want to increase. There is no option under 'Brightness & Color' available on 'System > Display', which just has 'Night light' and 'Color profile'.  There is a 'Brightness / Contrast' option on Display Manager, defaulting at 75% for both. When I use the slider to increase I get the message 'Adjusting to this value will increase power consumption above the default level. Do you want to continue', but there is no way I can see to press the 'Yes' button, as my cursor is inoperative. Please help!