Lost full screen on virtualbox

I updated my virtual box hosted ubuntu from Ubuntu version 20.10 to 21.04. Upon update, the Ubuntu is no longer in full screen.

Host: "20.04.2 LTS (Focal Fossa)" Virtualbox version: Version 6.1.16_Ubuntu r140961

I checked all the guest additions, x11 etc.. on the guest OS (V 21.04) all the good things still remain.

Please help get back the full screen.

Thanks in advance.