Bitcoin and cryptocurrency prices have struggled this week with the crypto market’s combined value slipping under $1.5 trillion—down from $2.5 trillion in May.

The bitcoin price, after getting an unexpected boost from Tesla billionaire Elon Musk last weekend, has resumed its decline over the last few days, falling back toward $30,000 per bitcoin.

Now, as bitcoin charts show the price 50-day moving average has fallen below the 200-day moving average—a pattern known as the “death cross”—Coinbase cofounder Fred Ehrsam has warned “most” cryptocurrencies and crypto-assets “won’t work” and “90% of NFTs” will have “little to no value in three to five years.”

Sign up now for CryptoCodexa free, daily newsletter that explains the world of bitcoin with brevity. Arriving in your inbox at 7am ET every weekday

MORE FROM FORBESBillionaire Bitcoin Investor Mark Cuban Calls For Crypto Regulation After Price Of Radical New Token Suddenly Crashes To Zero