This may be an authorization issue. However, it is more likely that your editing options are not set for deposits. In order to enter a bank deposit, the Document Type field must appear and must display a value of "ZK".
More info: The ZFB50ZK2 – Bank Deposit Journal Entry – Set Editing Options lesson walks you through the steps needed to change your editing options.
For additional assistance utilizing IRIS, please visit our instructional documents and videos on the IRIS Help website. You can also submit a help ticket online if you have additional questions.