The Verdict: Need More Info
Your own claim may not depend on your parent's loss at all. Find the date the loss was published and compare it with your birth: if you were born first, you can claim by descent now.
Brazil has no generational limit on descent. If your parent was Brazilian on the day you were born, you have your own claim, whatever happened to them later. Our citizenship by descent quiz covers it.
If the loss was published before your birth, your parent's nationality has to be restored first: by revocation where naturalising abroad was required of them, or by reacquisition otherwise, both decided by the Ministry of Justice.
If no declaration was ever published, your parent never lost anything. Loss was never automatic.