Anyone moving from crypto alerts to other markets hits the same surprise: the price looked like it crossed your level, but no alert came. Often the market was simply closed.
Crypto trades continuously, all weekend and all night. Gold and other metals futures trade almost around the clock from Sunday evening to Friday afternoon US time, with a short daily pause, and shut for the weekend. Major forex pairs run from Sunday evening to Friday evening US time and stop at weekends too.
An alert needs a live price to fire on. If gold gaps over the weekend, the alert fires when trading reopens, not before. If you need a level hit during a weekend, that is a crypto question.
The per-market pages at CoinPriceAlert state the trading hours next to the alert data, for example the gold page and the forex page.