I have managed to change all currency to id 1 as needed, but the error persists.
I don't understand this you tell me "A new table in ps 1.7.6 was ps_currency_lang. As the error in the 500 error post you link to is about the" locale.php "file, it is very likely that you are connected to it." So how should I disconnect?
what I did was a migration (not update) from 1.7.6.9 to 1.7.7.1 and I get that error when trying to enter the orders