Pretty link slug has http, not https

I currently run Pretty Links Pro 2.1.6.

We are moving over completely to https.

We are using an iis inbound redirect rule to change http to https. The rule we are using is below, and used everywhere for this purpose:
================================
<rule name=”HTTP to HTTPS redirect” enabled=”true” stopProcessing=”true”>
<match url=”(.*)” />
<conditions>
<add input=”{HTTPS}” pattern=”off” ignoreCase=”true” />
</conditions>
<action type=”Redirect” redirectType=”Found” url=”https://{HTTP_HOST}/{R:1}” />
</rule>
================================

When we turn this on, and someone clicks the pretty link in older content, (emails, blog posts, etc.) which starts with “http”, they simply go to the homepage, no redirection and nothing happens.

Pretty links seems to work only when the link begins with “Https”. This presents a problem as we cannot update much of the old content.

When I look at the pretty link slug, they all appear with only “http” and cannot be changed to “https”, which I thought could have resolved this.

In July Chrome will begin to act adversely with http websites, so we are trying to avoid http, and move over to https. I am currently forced to stop the http -> https redirect rule so that old content still works.

Is there anyway to resolve old http pretty links in content with https redirection?