Why “Not Working” as a Seed?

A valid BIP‑39 seed must use only words from the official list. This puzzle’s required letter‐lengths force words (like “mechanic,” “goose,” “error,” “amateur,” etc.) that aren’t in BIP‑39.

Conclusion:

The crossword puzzle cannot be perfectly solved with a 100% valid BIP‑39 seed.

The grid can be solved as shown (the “official” puzzle solution), but it won’t import into a wallet.

Or you can pick only BIP‑39 synonyms, but then they won’t match the letter layout given

You must choose one goal: a perfect crossword (which breaks BIP‑39) or a perfect BIP‑39 seed (which breaks the crossword layout). There’s no single solution that does both.