Error I cannot modify the store information

[sofysexshop]

Hello friends, I have a problem that I did not have before ... When I try to modify the store data, such as modifying the invoice header, I get this error:
Error
vmError: Registration failed: Username in use.
vmError: Save failed with the following error: Username in use.

https://www.sofysexshop.com/images/image_error.jpg
https://www.sofysexshop.com/images/image_config.jpg
https://www.sofysexshop.com/images/image_table.jpg

Please I need help to solve it, thank you very much and greetings. Attached images

[GJC Web Design]

check your joomla users  .. are u correctly registered etc and no duplicate user nanes?

[sofysexshop]

Thank you very much for your answer, I already found the error ... I had created a buyer field (identification number) and had put in the field name "id" this created a conflict in the tables of the database. **IMPORTANT**