A failed replication means that researchers attempted to recreate the results of a study but did not find support for the hypothesis in their results. Replications can be direct (trying to copy the original study's exact variables and design), or conceptual (generating a similar hypothesis but manipulating or measuring variables in a different way). A failed replication weakens the support for a theory, but it doesn't necessarily completely invalidate it. We shouldn't expect to see the same exact results in every sample of people we study, because people vary. With only one or two studies success or failure could be statistical chance, but by observing a pattern across many studies we can get a better sense of whether an effect really exists and how strong it might be. There has been a push for more replication in psychology in the last few years, because for a long time, unfortunately, replications weren't conducted often, in part due to poor incentives in terms of getting research published.
This isn't an area that I have experience with but maybe I can use this as an example when I discuss coding in a future video on research methods. Thanks for commenting!