The difference between both translations is the conjugation of the verb "ir" (to go), which is an irregular verb. "Fueron", the correct one, is in simple perfect preterit third person plural form, meaning the action occurred in the past and has ended since. "Iban" is in imperfect preterit third person plural meaning that the action started in the past but hasn't yet finished. Since we know they already didn't go to Paris, we must use "fueron"
