If you are repeating, you can register WITHOUT an add code two weeks before classes begin (as long as you are declared and in good standing).
If you can't register because your pre-requisites have not yet posted, contact the Registrar's office to find out how to make sure your graduation requirements are in MySJSU. You're going to have to do this at some point, so you may as well do it now, as it will continue to cause delays in registering for your classes.
If you are not yet declared in a major that requires Physics 50/51/52, you must first seek advising with the College of Engineering Student Success Center, or the College of Science Advising Center, before getting an add code.
Add codes do not override holds on your account; they can not allow you to register before your registration appointment window opens, and they are not needed for repeating.