Data not getting inserted in the database table

Here is my form, hitting submit is not storing the data in the database table. The table exists and the connection settings are correct

<table>

	[db_form]
	<tr>
		<th>First Name*</th>
		<th>Last Name*</th>
		<th> </th>
	</tr>
	<tr>
		<td>[input name="firstname"
			required="true"]</td>
		<td>[input name="lastname" ]</td>
		<td> </td>
	</tr>
	<tr>
		<th>Address</th>
		<th>Phone</th>
		<th>Email</th>
	</tr>
	<tr>
		<td>[input name="address" required="false"]</td>
		<td>[input name="phone" required="false"]</td>
		<td>[input name="email" required="false"]</td>
	</tr>
	<tr>
		<td colspan="3">[submit label="Register"]</td>
	</tr>
	[/db_form]
</table>

http://ww.wp.xz.cn/plugins/db-form/