Mac Mini and my LG 29Wk600 wide screen monitor

Okay folks I need your help.

I had been using my LG wide screen monitor with my 2018 MacBook Pro. I bought the screen because of the spilt screen compatibility (I do alot of Live streaming and need multiple windows open). Well

my laptop started acting up in November so I bought the mac mini and now my LG monitor works but I can't use the spilt screen. The icon is grayed out(like not loaded?) and it says no monitor connected. Well, I can see that the monitor is connected- its what I use everyday.

This is so frustrating and if I can't get it fixed I will have to return my mac mini. ughhhh.

Please help a girl out. I'm also ready to purchase a second monitor but am holding on that til I can get this fixed.

Thanks!

Mary