In the majority of ransomware cases the data is never returned to the victims, even when the ransom is paid.

If you have a source for that, I'd like to read it. I suspect this is pure speculation. From what I've read, anecdotally, paying the ransom usually does result in the data being recovered, because the attackers want to encourage others to pay. Obviously there are plenty of examples both ways and nobody seems to have any real statistics.

The best thing that can be done is contact your local authorities and let them advise you on the best steps to take next.

If you contacted the FBI, they would have advised you to pay the ransom (at least back in 2015). Even if they don't say that, they really can't help you recover your data in any other way, even if they wanted to (which they don't, because it's not their job at all).