Identity Management, NetID Activation Code Incorrect or Expired
Activation codes are used at the NetID Claim site, which guides incoming students through setting up their accounts: https://netidclaim.illinois.edu/
Detailed instructions for completing the Claim process can be found here: NetID Claim, How to Claim for Students
Activation codes must be used within a year. If you've deferred admission for longer than this, or if you're having any other trouble claiming your NetID, contact the department or college you were admitted to and request their assistance.
Undergraduate students with admissions trouble can ask for help at the Office of Undergraduate Admissions by email at admissions@illinois.edu or by phone at 217-333-0302. Graduate students can contact the Graduate College at grad@illinois.edu.
You can also contact the Technology Services Help Desk by email at consult@illinois.edu or by phone at 217-244-7000. They will be able to inspect your account and see what you need to do next.