First viewport had the unlocked symbol but would not allow me to bring up the scales list and/or change the scale. Before deleting first viewport I attempted several methods to make the viewport unlockable including highlighting it and clicking into it. These did not work. Therefore, I erased and drew a new viewport and found the problem was the same. I then looked for an alternative method to unlock viewports and found one in the ribbon bar that I have never used before. It worked. This is a solution but does not answer why the viewport appeared unlocked and was not.
And we will never know cause OR solution without a sample of the afflicted file.
It could have been this guy:
MAXACTVP (System Variable)
Sets the maximum number of viewports that can be active at one time in a layout.
Type: Integer
Saved in: Drawing
Initial value: 64
MAXACTVP has no effect on the number of viewports that are plotted.
Though I doubt it.