Ever since the Old Blood update, there exists a persistent bug while playing Mobile Defense on Earth.
If the player happens to come upon the tileset with a large elevated platform area in the middle and four big circular platforms beneath it, the Warframe will not be able to interact with the console to start the Mobile Defense countdown.
To be specific - the tileset is the same tileset which is the first mission objective on all Earth Sabotage missions.
Thank you for your attention.
EDIT: It seems the bug is platform-sensitive. While repeating the mobile defense mission, the data terminal appeared on a different circular platform. Here, my Warframe could interact with mild positioning issues.