The first thing you should do is check if you have actually submitted the application in question!
Look in your inbox for a confirmation email.
If you can't find one, neither in your inbox nor in your spam folder, you might have missed submitting the application.
If you attempt to submit the application again and receive a message that an application with your email already exists, it means the employer has received an application from you.
If you find a confirmation email, you can be assured that your application has been submitted.
The most likely scenario is that you submitted an application without being logged into your account. Even if you submitted it with the same email, the application will not be registered on your account if you weren't logged in, and it cannot be added afterward.
If you want additional confirmation that your application has been submitted, contact the employer!
If you are absolutely 100% sure that you were logged in when you submitted the application, perhaps you submitted it via another account?