Infinity Stones can’t work outside of their native reality in the comics, but they can in the MCU, indicating that Kang removed their power in Loki.
The MCU changed the rules for the Infinity Stones in Marvel’s Loki, and this was likely due to tampering by Kang the Conqueror, the true power behind the TVA. Following the Avengers’ time heist in Avengers: Endgame, Loki inadvertently reacquired the Space Stone (housed inside the Tesseract) but was quickly apprehended by the Time Variance Authority. In an equally dramatic and comedic moment, Loki learned that the TVA has plenty of Infinity Stones at their headquarters, but they lack power and are used by the staff as paperweights. At this point, Loki discovers that the TVA is perhaps a greater power than he could imagine, but comic fans were familiar with the limitations of the stones, as was Kang.
The latest episodes of Marvel’s What If…? seem to break the rules of these limitations by introducing a new version of Ultron. This iteration of the android killed Thanos and acquired all six Infinity Stones from him, using them to continue his genocidal mission across the multiverse, much to the surprise of some viewers and The Watcher. This reveals that, in the MCU’s multiverse, there are different rules for how the Infinity Stones work, which had to have been exploited by Kang in Loki to remove the stones’ potency in the TVA.