We bought NaviGo cards years ago on a trip to Paris...at least eight years ago. Will the same card work now?
If the Navigo card is less than 10 years old, theoretically it should still work. Paris Navigo cards have changed twice since 8 years ago (once in 2014 and again in 2018), so there's a chance older Navigo cards will not work.
Easiest way to check is to use a Paris transport ticket vending machine, place your Navigo card on the reader and see if the machine recognizes the card. It will give you recharge options on the display screen if the Navigo card is still recognized / valid. If it is not, the ticket vending machine will not give you any options.