How can I determine the type of line color set on a chartaxis in VBA?

How to check if a chartaxis line color is set solid line or gradient or automatic or no line on VBA

I tried this but does not seem to work

ax.AxisLine.Format.Line.Style = msoLineSolid

Can you modify this part of the code?

If you're looking to change the DashStyle or the Style :

Sub CheckChartAxisLineStyle()
    Dim ch As ChartObject
    Dim ax As Axis
    
    Set ch = ActiveSheet.ChartObjects(1)
    Set ax = ch.Chart.Axes(xlCategory) ' Change xlCategory to xlValue for value axis
    
    With ax.Format.Line
        .Weight = 10
        .DashStyle = msoLineDashDotDot
        .DashStyle = msoLineSolid
        .DashStyle = msoLineSquareDot
    End With
    Debug.Print ax.Format.Line.Style '1
    Debug.Print ax.Format.Line.DashStyle '2
    ax.Format.Line.Style = msoLineThickBetweenThin
    
End Sub 

For the DashStyle see documentation here and for the Style see documentation here

P.S. You probably don't want the .Weight at 10, that's just for example purposes :p

You can get the axis style like this:

charts("Chart1").Axes(xlPrimary).Format.Line.Style

The parameter for .Axes specifies which type of axes you want to access. A `XlAxisType' is needed. You can read about them here:
XlAxisType