<?elseif ($field=="EMAIL"):?><input type="text" name="ONE_CLICK_BUY[<?=$field?>]" value="<?=$value?>" id="one_click_buy_id_<?=$field?>" /> вот это замени на <?elseif ($field=="EMAIL"):?><input type="email" name="ONE_CLICK_BUY[<?=$field?>]" value="<?=$value?>" id="one_click_buy_id_<?=$field?>" required/>