VUM can't connect to vmware.com

I recently upgraded to VCSA 6.5. I've never used VUM, but I want to use it. VUM is unable to connect with VMware.com.

I'm using VMware VCSA 6.5.0-7312210

I've set the proxy server on the VCSA. When I test the connection, using the GUI, I get a message that says that Internet connection test can access http://www.microsoft.com, but not http://www.vmware.com.

When I look in the log file on the vcsa, I see messages like:

2018-01-12T04:47:03.038Z warning vmware-vum-server[7F12BD106700] [Originator@6876 sub=Default] File download error: downloading file: https://hostupdate.vmware.com/software/VUM/PRODUCTION/csco-main/csco-depot-index.xml failed, 0 bytes downloaded.. Retrying^M

But when I run "wget https://hostupdate.vmware.com/software/VUM/PRODUCTION/csco-main/csco-depot-index.xml" in /tmp, I get an xml file that is the same as running the wget on a Linux system in the same subnet:

<?xml version="1.0" encoding="UTF-8"?>

<vmwdpm:vendorList xmlns:vmwdpm="http://www.vmware.com/depotmanagement" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.vmware.com/depotmanagement ../../depot-index-xml.xsd">

    <vendor>

        <name>Cisco Systems, Inc.</name>

        <code>csco</code>

        <indexfile>csco-index.xml</indexfile>

        <relativePath>esx/csco</relativePath>

    </vendor>

    <vendor>

        <name>Cisco Systems, Inc.</name>

        <code>csco</code>

        <indexfile>csco-esx-index.xml</indexfile>

        <relativePath>esx/csco</relativePath>

        <content>

            <name>VMware ESX</name>

            <type>http://www.vmware.com/depotmanagement/esx</type>

        </content>

    </vendor>

</vmwdpm:vendorList>

Why is VUM running on the VCSA having trouble connecting to

  https://hostupdate.vmware.com

  http://vapp-updates.vmware.com

?