I'm encountering an error stating "NOT ALLOWED Sorry! You have no permission to view this page. Please contact the website administrator" when logging into SCA as a customer. The account is also missing from the header until I select a category then the account magically appears. When trying to checkout I encounter another error: "403 ERR_INSUFFICIENT_PERMISSIONS" when I try to checkout. Any idea how this would randomly happen?

As the error states, it's probably a permission problem. You should make sure that the customer is being assigned to the role required to view that page. If it is a new customisation, I would make sure that you've set the right permissions on the service that feeds it with data.

Thank you for your reply. The issue has something to do with customer segmenting function under the custom suitesuccess role. Reverting back to basic Customer Center fixed the issue for now.

OK, but if the SuiteSuccess team used a custom role for a particular customisation, I would try to find out why because while you have resolved this particular issue, you may have inadvertently broken another piece of functionality