Re-materialisation will not go through if the firm doesn’t respond, which happens if it is involuntarily delisted
The primary requisite to close a demat account is that the balance in the account should be nil. This means that you have to exit or transfer all the shares held in that account. Do check if you have shares of companies that are no longer listed in the market. The process to exit such shares is relatively easier in cases where companies delist from the stock exchanges voluntarily.