Django admin cannot changes in models apps

Hi all, I have a problem with Django Admin. I changed the file admin.py to display the models in the app, but the problem is that Django Admin doesn’t reflect the changes.
For example, I commented out this code:

admin.site.register(voucher.VoucherCustomer, VoucherCustomerAdmin)
#admin.site.register(Withdrawal, WithdrawalAdmin)

However, in the Django Admin interface, it still showed models app commented it.

On the other hand, I tried changing the name of the admin site header using admin.site.site_header, and it worked.
Thanks,

Please show the complete contents of that admin.py file.

Also, do you have multiple apps with admin.py files?

Sorry, I forgot have two admin.py files.

Thanks