This very much depends on the jurisdiction. Outside the US, some require you to provide electronic keys unconditionally in which case "I forgot" isn't a valid defense. Some let you off the hook if you forgot, but only if you can convince them that it's really true.

Then there's the US. Here, AFAIU the court can require you to hand over physical objects which it is certain actually exist. Failure to comply is contempt, and most states don't have a maximum for that (https://psmag.com/news/a-most-uncivil-contempt-3464).

For a password that's not written down, "I forgot" is indeed a valid defense here last I checked. Note that it doesn't apply if the court has a convincing reason to believe you were lying, which they would have in this case obviously.

However! It's more complicated that that here. Whether the court can demand things you know (ex passwords) as opposed to physical objects has historically been contentious. The trouble is that the fifth amendment protects you from being required to testify against yourself, and verbally providing a password seems an awful lot like testimony as it will presumably be used to incriminate you. It's gone both ways, and at some point the Supreme Court stated that a password was roughly equivalent to a physical key and so didn't qualify for protection. This ruling goes against (?) that, stating that it's equivalent to incriminating testimony and so can't be compelled.