Quick answer: Almost every failure is one of five things — the 48-hour window has passed, the code is full, a typo (O vs 0, I vs 1), you already redeemed a code, or Muse is not open in your region yet. If the code is the problem and your account is still inside 48 hours, claim a fresh code and redeem it immediately.
The code itself is done. Each invite code works for a limited number of people (about 20–30), and public codes get eaten fast. Retrying the same code will not help — get a different one. Also check the characters first: codes mix letters and digits, and O looks like 0, I looks like 1. Copy-paste instead of typing.
That means the account is out of its window: the Redeem field only exists in the first 48 hours after sign-up, and disappears permanently after one successful redemption. No code — ours or anyone's — can restore it for that account. What still works: share your own code and earn the same 1 billion tokens per person who redeems yours.
One redemption per account, for life. If you (or anyone on your account) already used a code, the bonus is already in your balance — check Settings → Usage.
Muse rate-limits the redeem field after repeated failures. Stop, wait a while, then make one careful attempt with a fresh code, pasted exactly. Do not burn your window guessing.
Muse is rolling out region by region — currently the US and Canada, 18+. An invite code does not override regional availability or a waitlist. If you are elsewhere, you will need to wait for your region to open; redeem a code within 48 hours of getting in.