How to start invoice number from 1?

[MrSteeiii]

When I try to change the invoice number to start from 1 in the back office, then I get error message "Invalid invoice number."

I want to start my shop, but the invoice number after my tests now is 7, I need it to start from 1. What is the way I can do that?

Also, need to mention that I did use the invoice number function to increase the invoice number from 5 to 7 as I did not understand at first that this function only works if I want to increase the number. 

I tried deleting orders, also changing database Tables ps_orders (column: invoice_number) and ps_order_invoice (column: number) to 0

Changing the database just made my back office not load so I changed everything back.

Any ideas? Why it is so hard?

 

[MrSteeiii]

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you may need to delete them or change their numbers in the database

In what rows do I need to do that? As I tried it and only what I got is that my orders was not opening just spinning. 

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I tried deleting orders, also changing database Tables ps_orders (column: invoice_number) and ps_order_invoice (column: number) to 0