We are not aware of any obligations that the bank has as to the matured CDs. If the customer has not chosen to renew, and the original agreement did not provide for automatic renewals, then the bank has no obligation to renew or pay interest on the deposits.
Note that under Regulation D, the bank will likely have to reclassify the accounts as demand deposits; any time deposit that has matured without being renewed is included in the definition of “demand deposit.” 12 CFR 204.2(b)(1)(vii). Specifically, the bank would have to reclassify any “time deposits upon which the contractually required notice of withdrawal as given and the notice period has expired and which have not been renewed (either by action of the depositor or automatically under the terms of the deposit agreement).” But again, the bank does not have any obligations to the customer after sending maturity notices for the accounts.