UpdateCursor with multiple loops in ArcPy

I have a feature class and I need to renumber from 1 and increase by 1 for a group of features. To do that, I need to define these groups (based on atributes of a field) and for each group make an update cursor.
My problem is that in my code, just the first group of features are updated and the others not. Where is my mistake?

This is what I have today

and this is what I want

My code:

import arcpy

lyrName = r"C:UsersMosheDocumentsArcGISDefault.gdbD1"
Layer = "Layer"
RefName = "RefName"
startNumber = 1
listValue = []


with arcpy.da.SearchCursor(lyrName, Layer) as cursor:
    for row in cursor:
        value = row[0]
        listValue.append(row[0])
    list = list(dict.fromkeys(listValue))
    print(list)

Layer2 = "Layer"
RefName2 = "RefName"
with arcpy.da.UpdateCursor(lyrName, [RefName2, Layer2]) as cursor2:
    for i in list:
        print (i)
        for row2 in cursor2:
                if row2[1] in str(i):
                    row2[0] = startNumber
                    startNumber = startNumber + 1
                    cursor2.updateRow(row2)
                    print "updated row {}".format(row2[0])
        startNumber = 1

import arcpy

lyrName = r"C:UsersMosheDocumentsArcGISDefault.gdbD1"    
fields = ["Layer", "RefName"]    
counter = 1
prevFieldValue = ""

with arcpy.da.UpdateCursor(lyrName, fields, sql_clause=(None, "ORDER BY Layer, RefName")) as cursor:
    for row in cursor:
        if row[0] == prevFieldValue:
            counter += 1
        else:
            counter = 1
        row[1] = str(counter)
        cursor.updateRow(row)
        prevFieldValue = row[0]