DropDown selection is showing ElementNotVisibleException.

I am tring to select one option from the dropdown box which has 211 items in to it, but the page is showing me the following error. It is in getSearchFilter function, option.sendKeys(Keys.ENTER); line.
org.openqa.selenium.ElementNotVisibleException: Element is not currently visible and so may not be interacted with
Command duration or timeout: 10.10 seconds

public class DataScreen {

@FindBy(xpath=Constants.datascreen)
public WebElement Data;
@FindBy(id = Constants.DataSearch)
public WebElement btnSearch;
@FindBy(xpath = Constants.NetworkSearch)
public WebElement drpNetwork;
@FindBy(id = Constants.DropNetwork)
public WebElement FltNetwork;
@FindBy(xpath = Constants.DrpACS)
public WebElement drpACS;
@FindBy(xpath = Constants.SelNetwork)
public WebElement selNetwork;
@FindBy(xpath = Constants.DropTaxid)
public WebElement Taxid;
WebDriver driver;
public DataScreen(WebDriver dr){
driver = dr;
}

public void getDataScreen(){
driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
Data.click();
btnSearch.click();
drpNetwork.click();
System.out.println("done with the Data screen loading");

}

public void getSearchFilter(){

Select sel = new Select(FltNetwork);
List<WebElement> network = sel.getOptions();
System.out.println("Networks " + network.size());

for(WebElement option : network){
System.out.println(option.getAttribute("value"));
if(option.getAttribute("value").equals("HPO")){
System.out.println("It is now HPO");
selNetwork.click();
option.getAttribute("value").equals("HPO");
option.sendKeys(Keys.ENTER);

}
}



HTML code :
<div id="prepay-datascreen-searchparameters" class="col-xs-12">
<div id="prepay-datascreen-searchnetwork" class="row">
<div class="col-xs-6">
<div class="row" data-bind="with: searchParameters">
<div class="form-group col-xs-6">
<select id="prepay-datascreen-searchnetwork-network" class="form-control" data-bind="options: networks, optionsCaption: 'Network', value: selectedNetwork" data-placeholder="Network" tabindex="-1" style="display: none;">
<option value="">Network</option>
<option value="ACPN">ACPN</option>
<option value="ACPNWC">ACPNWC</option>
<option value="ACS">ACS</option>
<option value="ACS30">ACS30</option>
<option value="ADIN">ADIN</option>
<option value="Align">Align</option>
-----------------------------------------------------------

<span class="select2-search select2-search--dropdown">
<span class="select2-results">
<ul id="select2-prepay-datascreen-searchnetwork-network-results" class="select2-results__options" role="tree" aria-expanded="true" aria-hidden="false">
<li id="select2-prepay-datascreen-searchnetwork-network-result-69nq-ACPN" class="select2-results__option" role="treeitem" aria-selected="false">ACPN</li>
<li id="select2-prepay-datascreen-searchnetwork-network-result-6avx-ACPNWC" class="select2-results__option" role="treeitem" aria-selected="false">ACPNWC</li>
<li id="select2-prepay-datascreen-searchnetwork-network-result-fzvx-ACS" class="select2-results__option select2-results__option--highlighted" role="treeitem" aria-selected="false">ACS</li>
<li id="select2-prepay-datascreen-searchnetwork-network-result-v3x4-ACS30" class="select2-results__option" role="treeitem" aria-selected="false">ACS30</li>
<li id="select2-prepay-datascreen-searchnetwork-network-result-jesn-ADIN" class="select2-results__option" role="treeitem" aria-selected="false">ADIN</li>
<li id="select2-prepay-datascreen-searchnetwork-network-result-fwye-Align" class="select2-results__option" role="treeitem" aria-selected="false">Align</li>
<li id="select2-prepay-datascreen-searchnetwork-network-result-92qn-AmericanPPO" class="select2-results__option" role="treeitem" aria-selected="false">AmericanPPO</li>