Attempt to lock a range of cells failing

[Ark68]

I'm not sure why, perhaps a second set of less fatigued eyes, can find the problem ...

I am getting an "Unable to set the locked property of the range class" error with the line in red. The sheet isn't protected, and I use this same code succesfully in other parts of the routine.

Sub reset_diamonds()
    
    Application.EnableEvents = False
    Application.ScreenUpdating = False
    
    Dim wshmain As Worksheet
    Set wshmain = Worksheets("Main")
      
    With wshmain
    
        .Unprotect
    
    'GROOMING
        With .Range("D24, E25") 'date, time
            .UnMerge
            .Value = "0"
            .Locked = False
        End With
        
        With .Range("D25, D26") 'qualifier, staff name
            .UnMerge
            .Value = ""
            .Locked = False
        End With
        
        With wshmain 'copy and paste shift formula (locked)
            Application.CutCopyMode = False
            Worksheets("Lists").Range("D31").Copy
            .Range("G26").PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, _
                SkipBlanks:=False, Transpose:=False
            .Range("G26").Locked = True
        End With
        
        With .Range("D24:G24, E25:G25, D26:F26")
            .MergeCells = True
        End With
        
    'PREPARATION1
        With .Range("K24, L25") 'date, time
            .UnMerge
            .Value = "0"
            .Locked = False
        End With
        
        With Range("K25, K26, K27") 'qualifier, staff, type
            .UnMerge
            .Value = ""
            .Locked = False
        End With
        
        With wshmain 'copy and paste shift formula (locked)
            Application.CutCopyMode = False
            Worksheets("Lists").Range("D31").Copy
            .Range("N26").PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, _
                SkipBlanks:=False, Transpose:=False
            .Range("N26").Locked = True
        End With
        
        With .Range("K24:N24, L25:N25, K26:M26, K27:N27")
            .MergeCells = True
        End With
                
    'SIGNATURE1
        With .Range("V24, U25") 'time, staff
            .UnMerge
            .Value = "0"
            .Locked = False
        End With
        
        With .Range("U24, U25")
            .Value = ""
            .Locked = False
        End With
        
        With wshmain 'copy and paste shift formula (locked)
            Application.CutCopyMode = False
            Worksheets("Lists").Range("D31").Copy
            .Range("X25").PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, _
                SkipBlanks:=False, Transpose:=False
            .Range("X25").Locked = True
        End With
        
        With .Range("V24:X24, U25:W25")
            .MergeCells = True
        End With
                
    'LIGHTS1
        With .Range("AC24, AC26") 'time on, time off
            .Font.Color = RGB(0, 0, 0)
            .UnMerge
            .Value = "0"
            .Locked = False
        End With
        
        'With .Range("AE25, AE27")
        '    .Font.Color = RGB(0, 0, 0)
        'End With
        
        With .Range("AB24, AB25, AB26, AB27") 'qualifier on, staff on, qualifier off, staff off
            .Font.Color = RGB(0, 0, 0)
            .Value = ""
            .Locked = False
        End With
        
        With wshmain 'copy and paste shift formula (locked)
            Application.CutCopyMode = False
            Worksheets("Lists").Range("D31").Copy
            .Range("AE25,AE27").PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, _
                SkipBlanks:=False, Transpose:=False
            .Range("AE25,AE27").Locked = True
        End With
        
        With wshmain.Range("AC24:AE24, AB25:AD25, AC26:AE26, AB27:AD27")
            .MergeCells = True
        End With
                
    'CLOSING
        With .Range("AI24, AJ25") 'date, time,
            .UnMerge
            .Value = "0"
            .Locked = False
        End With
        
        With .Range("AI25, AI26") 'qualifier, staff
            .Value = ""
            .Locked = False
        End With
        
        With wshmain 'copy and paste shift formula (locked)
            Application.CutCopyMode = False
            Worksheets("Lists").Range("D31").Copy
            .Range("AL26").PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, _
                SkipBlanks:=False, Transpose:=False
            .Range("AL26").Locked = True
        End With
        
        With .Range("AI24:AK24, AJ25:AL25, AI26:AK26")
            .MergeCells = True
        End With
           
    'Setup Detail
        With .Range("K29, K30, P33, P29:P32, K31:K33, K34, K35")
            .UnMerge
            .Value = ""
            .Locked = False
        End With
        
        With .Range("K29:L29, K30:L30, P33:Q33, K34:U34, K35:U35")
            .MergeCells = True
        End With
           
    'RELINE 1-4
        With .Range("I38, P38, W38, AD38, I39, P39, W39, AD39, I42, P42, W42, AD42")
            .UnMerge
            .Value = ""
            .Locked = False
        End With
        
        With .Range("I40, I41, P40, P41, W40, W41, AD40, AD41")
            .UnMerge
            .Value = "0"
            .Locked = False
        End With
        
        With wshmain 'copy and paste shift formula (locked)
            Application.CutCopyMode = False
            Worksheets("Lists").Range("D31").Copy
            .Range("K42,R42, Y42, AF42").PasteSpecial Paste:=xlPasteFormulas, Operation:=xlNone, _
                SkipBlanks:=False, Transpose:=False
            .Range("K42,R42, Y42, AF42").Locked = True
        End With
        
        With .Range("I40:K40, I38:K38, I39:K39, I41:K41, I42:J42, P38:R38, P39:R39, P40:R40, P41:R41, P42:Q42, W38:Y38, W39:Y39, W40:Y40, W41:Y41, W42:X42, AD38:AF38, AD39:AF39, AD40:AF40, AD41:AF41, AD42:AE42")
            .MergeCells = True
        End With
    
        .Protect
    
    End With
    
    Application.EnableEvents = True
    Application.ScreenUpdating = True
    
End Sub

I will appreciate any suggestions provided.

 

[shg]

Maybe try unmerging all cells before doing anything else.

Merged cells are their own punishment.