Hi there, liz2930.
It appears that you're not receiving a notification from the Capital One application on your iPhone 12. You've checked the notification settings in the app, have removed and redownloaded it as well. We understand how important it is to keep track of your spending, and we're glad to help with this.
Capital One Credit Cards, Bank, and Loans - Personal and Business -- Sign into your Capital One account, using a browser on your computer. Click "Need help?" at the top of the page, and type "alerts" at the bottom of the pop-up. Select "Manage Alerts", then the pencil to the right of Account Alerts. Capital One only sends an email or SMS message to your iPhone based on the alerts/levels you set. The same alerts are provided on your iPhone as well. You can view them there by selecting your profile > Alerts & Notifications.
Take care.