When all icons on the View Control Bar are dimmed (disabled), including the View Scale, it typically means the view is being controlled by a View Template. View templates apply standardized settings---such as scale, discipline, detail level, and more---across multiple views to ensure consistency. However, these templates can lock certain parameters, including the view scale, preventing manual changes.

According to Revit Electrical Design standards:

'If a view is governed by a View Template, properties such as view scale may be locked and appear dimmed in the View Control Bar. To regain control and allow changes like adjusting the view scale, the view template must be removed. This is done by setting the View Template to <None> in the Properties Palette.'

Steps:

Select the view in question.

Open the Properties Palette.

Locate the View Template parameter.

Set it to <None>.

Now the View Control Bar becomes active and the scale can be changed freely.

Clarification of Other Options:

B (Edit the assigned view template): Changes apply to all views using that template, not just the one.

C (Duplicate the view with Detailing): Creates a copy but doesn't resolve template restrictions.

D (Right-click on the scale and select <Activate>): This is not a valid method in Revit.

Reference: This explanation aligns with the View Template behavior documented in Revit MEP and Electrical modeling workflows.