on both pages, there is no form around the add to cart button code.
for example, on the internal.php page, the add add top cart form:
<table width="600" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
<td width="138" rowspan="2" align="left" valign="top" bgcolor="#FFFFFF"> </td>
<td width="462" align="left" valign="top" bgcolor="#FFFFFF"><p align="left"><?php echo $row_rsInternal['ITEM']; ?><br />
$<?php echo $row_rsInternal['PRICE']; ?> <br />
<input type="hidden" name="cupcake1_11_ID_Add" value="<?php echo $row_rsInternal["PRODUCT_ID"]; ?>" >
<input type="text" name="cupcake1_11_Quantity_Add" value="1" size="4" >
<input type="submit" class="eC_FormButton" value="Add to Cart" name="cupcake1_11_ATC"><br />
</p></td>
</tr>
<tr>
<td align="left" valign="top" bgcolor="#FFFFFF"> </td>
</tr>
</table>
does not have a form tag around it, the form tag is missing. for a form to bale to submit, there must be a form tag:
<form action="<?php echo ($_SERVER["PHP_SELF"].(isset($_SERVER["QUERY_STRING"])?"?".htmlentities($_SERVER["QUERY_STRING"]):""));?>" method="post">
<table width="600" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
<td width="138" rowspan="2" align="left" valign="top" bgcolor="#FFFFFF"> </td>
<td width="462" align="left" valign="top" bgcolor="#FFFFFF"><p align="left"><?php echo $row_rsInternal['ITEM']; ?><br />
$<?php echo $row_rsInternal['PRICE']; ?> <br />
<input type="hidden" name="cupcake1_11_ID_Add" value="<?php echo $row_rsInternal["PRODUCT_ID"]; ?>" >
<input type="text" name="cupcake1_11_Quantity_Add" value="1" size="4" >
<input type="submit" class="eC_FormButton" value="Add to Cart" name="cupcake1_11_ATC"><br />
</p></td>
</tr>
<tr>
<td align="left" valign="top" bgcolor="#FFFFFF"> </td>
</tr>
</table></form>