A conviction can be reversed on appeal if the evidence at trial is clearly not sufficient to establish the elements of the crime. In Jackson v. Virginia (1979), the Supreme Court made this a federal constitutional rule. Suppose (1) the elements of a crime are A, B, and C; (2) the judge erroneously instructs the jury they must find A, B, C, and D; (3) on appeal the appellate court finds plenty of evidence to support elements A, B, and C but none on D. Is that reversible Jackson error? No. Jackson concerns only what the elements the jury should have been instructed on, not what they were instructed on.
If the defendant didn't raise a statute of limitations defense at trial, can he raise it on appeal? Not unless Congress has made the time limit jurisdictional, which it rarely does and did not do for the crime involved in this case. How about the plain error rule? No. If the defendant does not bring it up, the failure of the trial court judge to do so sua sponte is not error, plain or otherwise.
That's the short version. For a longer version, see Rory Little's post at SCOTUSblog.