Basic level TradingView users are only allowed up to (1) alert per chart. There are tiered plans with TradingView that provide more alerts:
Use the desired settings of notification upon bar code, only once, once per bar, or once per minute. You may also get notified by other actions, and design the message of the alert. (Free accounts may have limits of certain Alert Actions).
You can change your alert to: Alert only once, once per bar close, once per bar, or once per minute. We recommend ONCE PER BAR CLOSE.