I have an I pad pro that I am using for grad school. I frequently use split screen, but yesterday it stopped working. I tried restarting, going to settings to see if there was an allow multitasking button to toggle but I didn't see it. The only option when I click the 3 dots at the top of any page now is to add another window.
iPad Pro (4th generation)
If you don't see the Multitasking Split View or Slide Over options in the Multitasking menu, ensure that you have not enabled Stage Manager:
Settings > Home Screen & Multitasking > Stage Manager > Use Stage Manager on iPad - set to OFF
If you don't see the Multitasking Split View or Slide Over options in the Multitasking menu, ensure that you have not enabled Stage Manager:
Settings > Home Screen & Multitasking > Stage Manager > Use Stage Manager on iPad - set to OFF
I had the same problem right after I updated but I hard-resetted my ipad and it worked. So maybe try that.
I pad pro split screen not working after ios 16.5
