Help with VIEWS

Hallo,
I am SUPER CONFUSED with the view mode…I’ve read all the forums but still confused…
I now can not have (on A320NX) the upper panel (CTRL +8) : if I keep both pressed it stays if not gets back to main panel (while before just pressing CTRL+8 was taking me to upper head panel and stay there, now it gets back…)…teherefore I have “lost” all the pre-established panels (i.e CTRL +5 MCDU and so on…)… of course I know that with CTRL+ALT + Number I can establish personalised views but how do I recover those already set up by deafult, what have I done wrong, what should I check in CONTROLS command?
Thanks for help