If I undertand correctly, you were granted the student visa after showing migraciones that you had sufficient funds in the bank to support yourself while you are "studying" in Argentina, and migraciones did not actually require that you demonstrate that you have a current source of income (even if you do).
One of the requisites of citizenship is that you can demonstrate "an honest means of living." Simply having money in a bank will not fulfill that requirment. The court wants to see that you have a source of income and that it is not generated by criminal activity.
The income can be from a foreign source, such as Social Security, or income generated in Argentina, such as teaching English, as Bajo_cero2 indicated.