There Is No Single Word List
Scrabble in North America runs one tournament list, Scrabble in most of the rest of the world runs a different and larger one, Words With Friends runs its own, Wordfeud runs another, and Wordle answers come from a hand-curated list of a few thousand common words rather than from any dictionary at all. A word can be perfectly real and still be absent from the particular list your game is checking against.
What Usually Causes It
Proper nouns are out of almost every list. So are abbreviations, hyphenated forms, and anything with an apostrophe. Recent slang lags by years because lists are revised on a schedule. And regional spelling cuts both ways: words that are standard in British English are missing from the North American list and the reverse.
What To Do About It
Settle it rather than argue about it. Check Dictionary tells you whether a word is in the list this site uses, which covers 269,870 words, and links the Merriam-Webster entry so you can see whether it is a real word that is merely absent from a game list. Those are two different questions and most arguments are about confusing them.
More like this in the guides index, or put your own letters into the Word Unscrambler.