Dates Not working in a userform comobox

Add the below piece of code:

Private Sub ComboBoxFind_Change()
    ComboBoxFind.Value = Format(ComboBoxFind.Value, "dd/mm/yyyy")
End Sub

Making your code:

Private Sub ComboBoxFind_Change()
    ComboBoxFind.Value = Format(ComboBoxFind.Value, "dd/mm/yyyy")
End Sub

Private Sub CommandButton1_Click()
    Dim TargetRow As Integer
    
    TargetRow = Application.WorksheetFunction.Match(CDbl(ComboBoxFind), Sheets("Moorhouse").Range("RentFindAmend"), 0)
    MsgBox TargetRow
End Sub

Hello. Another approach would be to leave the following in the userform:

Private Sub UserForm_Initialize()
ComboBoxFind.RowSource = ""
ComboBoxFind.List = Range("RentFindAmend").Value
End Sub

Private Sub CommandButton1_Click()
Dim TargetRow As Long
TargetRow = Application.WorksheetFunction.Match(CDbl(CDate(ComboBoxFind)), Sheets("Moorhouse").Range("RentFindAmend"), 0)
MsgBox TargetRow
End Sub