Split View Not Working All Of A Sudden

I'm using MacOS Big Sur on my MacBook Air, and have been using the split view option just fine before. Now all of a sudden it stopped working, I can't split my screen with MS Office Apps, Preview, iWork, Zoom... Nothing. I've tried the Mission Control option -it already is checked. Tried restarting. I don't understand what is the problem.. I work from home and need my screen split almost all the time. Need help in this department ..