From your linked article:
“We as a government have sought to bring Paul Whelan home as well. We did so in good faith with the Russians and proposed multiple different options. Regrettably, due to the nature of the sham espionage charges Russia levied against Paul, the Russians have treated, continue to treat, his situation differently from Brittney’s and rejected each and every one of our proposals for his release.”
And
“The White House in April was able to free former Marine Trevor Reed as part of a prisoner exchange for a Russian citizen, Konstantin Yaroshenko, who had been serving out a 20-year sentence on drug charges.”