Error Code -9 Not showing again

Thank you for your report!
However, this issue is Working as Intended.

The report you have submitted is working as intended: Per the 1.16.1.61 changelog the -9 error should not show when launching the game offline, excerpt below.

Fixed account error number -9 being displayed when launching the game while signed into an account, but no network connection

Please note, that mechanics of the game may change between updates.
Things such as graphics, sounds, world creation, biomes, redstone, villagers, and animals may not work the same in current versions.

Full Version History – Snapshot Version History – Feature Requests and Suggestions

Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – ✍️ Feedback and Suggestions – 📖 Game Wiki