Isla Sorna continued to function until Hurricane Clarissa hit the island. All personnel were evacuated from the island and the facilities were later abandoned. However, before they left, the InGen personnel unlocked the gates of the island's enclosures so that the dinosaurs could have a better chance of surviving the storm. Within a few years, the dinosaurs took over the island and established a fully functional ecosystem.
The island was finally de-populated in 2004 when all the animals were transferred to Isla Nublar.
However, things don't add up. It is said that:
"The new species were grown in secret on Isla Sorna (Site B) and experimented on over a period of nine months, starting just 100 days after the company was bought by Masrani Global."
Only problem is Marsani bought InGen after John Hammond passed away in 1998, long after the hurricane had destroyed it (allegedly it hit Isla Sorna in 1993 right after the Isla Nublar incident).
And we also know from Jurassic Park III that in 2001 it was completely abandoned and restricted.
Check out the reports from the Dinosaur Protection Group.