Not able to access LSC trial ORG

That specific error, 'No assigned org found for the provided email and event code,' almost always means you are going through the sign-up flow again for an org that already exists, rather than just logging into it. A sign-up link / event code is one-time: it provisions the org once and will not re-run, and extending the org's expiration does not re-arm the sign-up link. So the flow you used to create it originally will not work a second time. 

Two things to try: 

1. Do not re-sign-up, log in directly. Go to

(or the org's My Domain URL if you have it) and sign in with the username you created for that LSC org (usually your email with a suffix, and the org has its own password). If you do not remember it, use 'Forgot Your Password' on that login page against the username. The org still exists (it was extended to 2027), so direct login is the path, not the sign-up link. 

2. Confirm you are using the exact email the username is tied to. The error keys on 'email + event code,' so an alias or different-case email will not match. 

If direct login genuinely fails (the username is not recognized at all), then the org may have been unassigned on the backend despite the extension, and re-signup cannot fix that. In that case escalate back through the SAME Partner Support channel that extended it to 2027 (not general Trailhead support), and give them the org Id and the original sign-up/event details, they can see whether the org is still assigned to your Trailblazer account. 

Most likely it is number 1 though, the org is fine and you just need to log in directly instead of re-running sign-up. 

Hope that gets you back in!