'COLLAPSED' WORKSPACE BACKGROUND in PS [2020]

[MF-UK]

I work on an iMac and all my images are edited in LR and then ‘finished’ if needed in PS. Whether the image is brought in directly via LR or even from , say my desktop, the image opens WITHOUT the base background appearing. Tool bar, history and layers panel all there.
So in order to view the image on PS's background [default, black, dark grey etc.] every time I have to pull and drag the corner of the said workspace background, to get the maximum image filling my screen.

HELP! please.. and thanks to all inadvance 

[MF-UK · Accepted solution]

Just watched a vid on YouTube and have discovered that Application Frame in 'Window' wasn't ticked! so re ticking has restored my interspace/workspace to full screen - phew, everything back to normallity