Thank you for your answer @kennethsequeira. I think I have might found the cause the problem.
When I setup a new Company the default country is Greece (though in Company Customize Form I have not a default value for the field country). But the Greek Chart of Accounts is in the unverified folder, so it is not loaded ( I would like to know how to load an unverified Chart of Accounts).
The thing is that when I setup a new company the default value for field country is always Greece.
So I chance the country to Germany for example, but the verified German chart of accounts is not loaded (it behaves as if the country was set to Greece).
Only when I change the default field country value to Germany from Company Customize Form the German Charts of Accounts are loaded.
Is this behavior correct? I don’t think so. When the value of country in Company is changed, the corresponding country Charts of Accounts should be loaded.
Do you have any solution for that?