Joyce and Hopper visit HNL and don't see any sign of activity. They simply see the concrete-covered wall where the Gate used to be.
But we know the Russian lab entrance is far beneath the Starcourt mall, and then a long hallway leads to the place where the Gate is. But where is this new Gate in relation to the rest of Hawkins?
"In Hawkins, this door had been opened once," Murray says while interpreting for Alexei. "It was still healing."
This makes it sound like it's the same place where the first Gate was, but if it is then we're confused as to how the US government hadn't realized so much energy-related activity was happening underneath the HNL.