---
title: "SCORM error library — the errors your package throws, explained | SCORM Lab"
canonical_url: "https://scorm-lab.com/errors"
last_updated: "2026-09-22T15:37:54.151Z"
meta:
  description: "The recurring SCORM errors visitors hit inside their own packages in SCORM Lab: what each one means, which authoring tool produces it, and how to fix it."
  "og:description": "The recurring SCORM errors visitors hit inside their own packages in SCORM Lab: what each one means, which authoring tool produces it, and how to fix it."
  "og:title": "SCORM error library — the errors your package throws, explained"
  "twitter:description": "Free in-browser SCORM debugger. Drop a SCORM 1.2 or 2004 .zip to inspect the API transcript, CMI data model, sequencing and lint. Nothing uploaded unless you choose to share."
  "twitter:title": "Debug any SCORM package in your browser, free"
---

# The errors your package throws, explained

These are not findings from SCORM Lab's own checks (see [authoring checks](https://scorm-lab.com/lint) for those) — they are errors packages throw at themselves: a wrapper library's console message, or a raw SCORM API error code, while the course plays inside the Lab. Each page below opens with the exact error text, so if you searched it you should land straight on the right one.

- [Initialize called twice in the same launch `SCORM Error 101: LMS was already initialized!`The course opened its SCORM session twice. "LMS was already initialized!" is the runtime's own diagnostic for a second Initialize call, not custom course text.](https://scorm-lab.com/errors/lms-already-initialized)
- [A SCORM 1.2 package asking for the SCORM 2004 element cmi.learner\_id `SCORM Error 101: The data model element passed to getCMIValue (cmi.learner_id) is not a valid SCORM data model element`The package is running as SCORM 1.2 but its wrapper is reading a SCORM 2004 element name. SCORM 1.2 calls the same idea cmi.core.student\_id.](https://scorm-lab.com/errors/cmi-learner-id-invalid-element)
- [session\_time written in the wrong SCORM version’s format `SCORM Error 405: Incorrect Data Type [Element: cmi.core.session_time]`cmi.core.session\_time was written in the SCORM 2004 ISO 8601 duration format on a SCORM 1.2 package. 1.2 expects HHHH:MM:SS.SS; the write is rejected outright.](https://scorm-lab.com/errors/session-time-incorrect-data-type)
- [cmi.core.score.scaled — a SCORM 2004 element on a SCORM 1.2 path `SCORM.data.set('cmi.core.score.scaled') failed`cmi.core.score.scaled mixes a SCORM 1.2 path (cmi.core.score.\*) with a SCORM 2004-only leaf (scaled). It doesn't exist in either edition as written.](https://scorm-lab.com/errors/score-scaled-not-supported)
- [Storyline output throwing on a null classList `Uncaught TypeError: Cannot read properties of null (reading 'classList')`A Storyline HTML5 player script reached for classList on an element that isn't in the page. Usually a missing or renamed player asset, or the SCO launched outside its own story.html frame.](https://scorm-lab.com/errors/storyline-cannot-read-classlist)

Run the package that's throwing one of these in [SCORM Lab](https://scorm-lab.com/) — the Transcript and Console tabs show exactly where it fires. It's free, runs entirely in your browser, and nothing is uploaded unless you choose to share it.

Still stuck after the fix? Bring the package to a [SCORM consult](https://calendar.lostendfound.com/larry/scorm-consulting).