WARNING: Spoilers ahead for Space Force season 2.
Spencer House did not return in his role of security guard Duncan Tabner in Space Force season 2. The Netflix comedy series, starring Steve Carell and John Malkovich in the respective main roles of Space Force general Mark Naird and lead scientist Dr. Adrian Mallory, was co-created by Carell and Greg Daniels. Most of the Space Force cast returned for season 2 — so why didn't House?
In Space Force season 1, Duncan Tabner was involved in the security aspects of the Colorado Space Force base. Tabner was particularly respectful of his role, refusing to let anybody in unless they showed the proper ID, and that resulted in particularly funny interactions, especially when his refusals were aimed at people he would have definitely known, such as Dr. Mallory or Air Force General Kick Grabaston (Noah Emmerich). Towards Space Force season 1’s end, he was introduced as a potential love interest for Erin (Diana Silvers), General Naird’s daughter.
Space Force season 2 opened with the investigation into Naird and his subordinates, as they had refused to attack the Chinese base on the moon in the Space Force season 1 finale. As Tabner tried to refuse to let General Grabaston in, it would have made sense if he, too, would have been investigated like the rest of the group. Instead, Spencer House's character Tabner wasn't even mentioned in the Space Force season 2 premiere, and the reason why isn't clear.
Although mostly appearing in his role of a security guard, Tabner’s other main storyline involved Erin in Space Force season 1. After realizing they had left their mark on the other, as they both remembered bits of information about the other person, they started spending more time together. That seemed to come to an end when Tabner started reading to impress Erin, only for her to realize he was reading up conspiracy theories on dubious websites. When Erin was interviewed over her father’s insubordination and fitness to lead, she talked about dating someone in the Space Force who was probably a Russian spy, Yuri "Bobby" Telatovich (Alex Sparrow), without even mentioning Tabner.
While no clear explanation was given for House not reprising his role as Duncan Tabner, it’s possible he might come back for Space Force season 3 if it were renewed. As General Naird and his team did not lose their jobs or end up arrested, it’s plausible that Tabner wasn’t either, especially as Grabaston was punished and had to retire from the Air Force at the beginning of season 2. With Space Force surviving but with a halved budget, it’s also equally possible that Tabner was fired. Still, were Tabner to come back to Space Force in season 3, it can be hoped that it would be in a capacity that makes the Alabama security guard shine.