I have a Visual Force page that I created that contains a dynamic pick list field I want to add to a page layout. The VF page uses a standard controller for "Account" and has an extension. I am having an issue with the dynamic pick list field displaying on the Account page when I add it to the page layout.

VF Code:

<apex:page standardController="Account" extensions="Account_QuoteTemplatesExtension" showHeader="false" sidebar="false">
    <apex:form >
        <apex:PageBlock mode="edit">
            <apex:PageBlockSection title="Quote Template Selection" columns="1">
                <apex:PageBlockSectionItem >

                    <!-- Label for picklist -->
                    <apex:outputLabel value="Quote Template" for="quoteTemplates" />
                    <!-- Dynamic picklist of values (quote templates) -->
                    <apex:selectList value="{!selectedTemplate}" size="1" id="quoteTemplates">
                        <apex:selectOptions value="{!TemplateOptions}" />
                    </apex:selectList>

                </apex:PageBlockSectionItem>
            </apex:PageBlockSection>
        </apex:PageBlock>
    </apex:form>
</apex:page>

Apex Controller:

global with sharing class Account_QuoteTemplatesExtension {

private final ApexPages.StandardController controller;
private final Account record;
private final Id recordId;

public String selectedTemplate {get; set;}

public Account_QuoteTemplatesExtension (ApexPages.StandardController stdController) {
    this.controller = stdController;
    this.recordId   = this.controller.getId();
    this.record     = [SELECT id, name FROM Account WHERE Id = :this.recordId LIMIT 1];
}

// Returns list of quote template options
public List<SelectOption> getTemplateOptions() {
    // Initiate option list
    List<SelectOption> tempOptions = new List<SelectOption>();
    // Get all quote templates from metadata
    List<Quote_Template__mdt> quoteTemplates = [SELECT MasterLabel, Template_Id__c FROM Quote_Template__mdt];
    // Add all options to select option list
    for (Quote_Template__mdt temp : quoteTemplates) {
        tempOptions.add(new SelectOption(temp.Template_ID__c,temp.MasterLabel));
    } 
    return tempOptions;   
}

I added the VF page in a section on the page layout like so:


But the page layout section remains blank


The preview renders properly, but it will not display on the page layout


I have already checked the security settings for the VF Page and have enabled access for System Administrator, which is the profile I am using. I have also tried to render a very simple VF page with the following code:

<apex:page standardController="Account">
        <apex:outputText value="Hello World" />
</apex:page>

But it still leaves the page layout blank-- I'm not sure where to go from here. Any suggestions?