You need to liberate more territory before you can begin the next mission. Once you’ve cleared enough territory, head to the power plant on the northwest side of Vis Electra. After the cut scene at the beginning of the mission, follow the glowing power conduits to the rocks ahead, then climb over the rocks to the next batch of cables.
When you reach the cliff above the town head over to the settlement and rejoin the conduits on the far side of the area. Use your grapple to take to air and head down the large hill as you follow the cables into the water and out the other side. Follow the coastline as the pipes will not be visible throughout the entire journey. When you finally reach the patrol boat, drop down to the ground below to the checkpoint and take out the boats and guards within.
Head into the facility and head to the next marker, which is the underground entrance. Swim through the entrance and into the cavern ahead, then follow the path and ignore the men in the next room as you search for the power node down the way.
Move over to the gate blocking your way and hack the controls to continue. Clear everything involved with the power node using explosives or whatever means of destruction you have available to you. There are a few soldiers here that you may need to take down as well, so be ready for the engagement.
Once you’ve destroyed the power node head out of the plant to complete the mission. Head northwest to find the Turncoat mission and continue with the story.