Split screen in android is not working in same level

hi, i am not able to get split screen in android but it is working is system.I have 2 issues

once you can see screenshots

1)this is from system preview and it is working fine

the above is from mobile preview and left screen is coming black

2)I am getting this error after closing viewport preview

this is blueprint i made for splitscreen and error throwing here

please share any solutions for these