Error setting stack by kernel

Question

I always thought I understood about the stack but I realized that no, I’m wanting to understand the stack in practice, so I created this environment

The idea is to set the top of the stack at 7FFFh address because from 8000h onwards is the kernel, after that I will put something in the stack so it will be at address (7FFFh - 2 = 7FFD) since I am in real mode, I will try to access the location by physical address

more when I call the label Configstack it does not work, I did several tests and if I do not call this label everything works normally

[bits 16]
[org 0x8000]

call Main
call End

Main:
    call ConfigStack
    call SetSegment
    call SetVideoMode
    call ClearScreen
ret 

ConfigStack:
    mov ax, 07E0h
    mov ss, ax
    mov sp, 1FEh
ret 

Note: it calls all other labels including End, but I will not show the code because the problem is in Configstack

Clearscreen leaves the screen green to make sure that I have entered the kernel and that it executes all the other Abels, as I said everything works if I do not call Configstack

The stack segment is 07E0h because the bootloader ends in one byte before

| 7C00h | - Beginning of the Bootloader

|--------| - 512 bytes

| 7DFFh | - End of the Bootloader

| 7E00h | - Pile start

| ------ | - 512 bytes

| 7FFFh | - Bottom of the pile

| -------|

| 8000h | Kernel start