At this point, your registration window will no longer be active. You will need to go through the process of applying as a Guest Student. It's likely that you will be assigned the same FlashLine ID as the registration system will recognize that it has you on file.
There is no penalty. Guest Student admissions are temporary, one-semester admissions.
If you do not register during that semester your admission status will become inactive and, if you wish to attend at a later date, you will need to complete the Guest Student application process again.
Contact the Admissions Office and let them know you wish to change your start date from Fall to Summer. You may need to speak with your advisor as well. If you have not yet been assigned an advisor or participated in Destination Kent State, you can contact 330-672-2014 or email@example.com.