Thanks for your continuing help. I have just solved the issue and believe Autocad need to be aware of the reason for the problem Ive been trying to overcome.
As per an earlier posted response I tried several things buit could not resolve the probelm on my desktop but, as described, I could open the files as they should open on my previous laptop.
My desktop has the taskbar at the bottome of the screen and so that I could get a full page in Fusion, this taskbar was set to automatically hide in Windows 10 settings. To make sure this could not be a problem I moved the taskbar to be on the right hand side of my screen. Lo and behold, all my Fusion files work with the timelines and view commands visible!
Windows 10 had carried out an update and I now fel certain that a result is that even when the Taskbar is not visible at the base of my sceen nothing else can be visible either so the base just looks empty as you saw in the screenshot I added to the thread.
So help much appreciated and I hope my findings help othr who, I'm sure, will encounter a similar problem if their Taskbar is set to not visible.