Office Regex not underlining anything - outlook

Question

I'm building an outlook addin (running it locally, not through web) that should detect certain words when a user is composing messages. I started with the basic example here. Then modified the manifest to instead work on "compose" based on the differences in this tutorial.
From what I've read, all I have to do to have it underline a regex match is to add a rule to detect the thing I want to detect in the manifest. Once detected, the user should be able to click on it and I can have it do anything I want, but I can't even get it to detect the regex. The keyword I'm looking for is based on the example ticker symbol, but I simplified it to just look for "NYSE"
In the manifext.xml below, I have code to add a taskbar and a button but I haven't coded them to do anything, they just appear in the ribbon when I compose a message. I did this just so I could have a visual indication that something was working. These do appear, but still the regex is not underlining the keyword "NYSE". What am I missing here?
Here is my manifest.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0" xmlns:mailappor="http://schemas.microsoft.com/office/mailappversionoverrides/1.0" xsi:type="MailApp">
<Id>123456789123456789123456789</Id>
<Version>1.0.0.0</Version>
<ProviderName>Me</ProviderName>
<DefaultLocale>en-US</DefaultLocale>
<DisplayName DefaultValue="composeTest"/>
<Description DefaultValue="My Compose Add-in based on the template"/>
<IconUrl DefaultValue="https://localhost:3000/assets/icon-64.png"/>
<HighResolutionIconUrl DefaultValue="https://localhost:3000/assets/icon-128.png"/>
<SupportUrl DefaultValue="https://www.contoso.com/help"/>
<AppDomains>
<AppDomain>https://www.contoso.com</AppDomain>
</AppDomains>
<Hosts>
<Host Name="Mailbox"/>
</Hosts>
<Requirements>
<Sets>
<Set Name="Mailbox" MinVersion="1.1"/>
</Sets>
</Requirements>
<FormSettings>
<Form xsi:type="ItemRead">
<DesktopSettings>
<SourceLocation DefaultValue="https://localhost:3000/taskpane.html"/>
<RequestedHeight>250</RequestedHeight>
</DesktopSettings>
</Form>
</FormSettings>
<Permissions>ReadWriteItem</Permissions>
<Rule xsi:type="RuleCollection" Mode="And">
<Rule xsi:type="ItemIs" ItemType="Message" FormType="Compose"/>
<Rule xsi:type="ItemHasRegularExpressionMatch" PropertyName="BodyAsPlaintext" RegExName="TickerSymbols" RegExValue="NYSE\b"/>
</Rule>
<DisableEntityHighlighting>false</DisableEntityHighlighting>
<VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides" xsi:type="VersionOverridesV1_0">
<Requirements>
<bt:Sets DefaultMinVersion="1.3">
<bt:Set Name="Mailbox"/>
</bt:Sets>
</Requirements>
<Hosts>
<Host xsi:type="MailHost">
<DesktopFormFactor>
<FunctionFile resid="Commands.Url"/>
<!-- This is a COMPOSE addin, so we want the button(s) to appear when the compose windoe(s) are opened -->
<ExtensionPoint xsi:type="MessageComposeCommandSurface">
<OfficeTab id="TabDefault">
<Group id="msgComposeGroup">
<Label resid="GroupLabel"/>
!-- First button opens task pane (is this needed in my app???) -->
<Control xsi:type="Button" id="msgComposeOpenPaneButton">
<Label resid="TaskpaneButton.Label"/>
<Supertip>
<Title resid="TaskpaneButton.Label"/>
<Description resid="TaskpaneButton.Tooltip"/>
</Supertip>
<Icon>
<bt:Image size="16" resid="Icon.16x16"/>
<bt:Image size="32" resid="Icon.32x32"/>
<bt:Image size="80" resid="Icon.80x80"/>
</Icon>
<Action xsi:type="ShowTaskpane">
<SourceLocation resid="Taskpane.Url"/>
</Action>
</Control>
<!-- This button calls a function named "Action" as described below -->
<Control xsi:type="Button" id="ActionButton">
<Label resid="ActionButton.Label"/>
<Supertip>
<Title resid="ActionButton.Label"/>
<Description resid="ActionButton.Tooltip"/>
</Supertip>
<Icon>
<bt:Image size="16" resid="Icon.16x16"/>
<bt:Image size="32" resid="Icon.32x32"/>
<bt:Image size="80" resid="Icon.80x80"/>
</Icon>
<Action xsi:type="ExecuteFunction">
<!-- "action" is the name of the function to run when this second button is clicked -->
<FunctionName>action</FunctionName>
</Action>
</Control>
</Group>
</OfficeTab>
</ExtensionPoint>
</DesktopFormFactor>
</Host>
</Hosts>
<Resources>
<bt:Images>
<bt:Image id="Icon.16x16" DefaultValue="https://localhost:3000/assets/icon-16.png"/>
<bt:Image id="Icon.32x32" DefaultValue="https://localhost:3000/assets/icon-32.png"/>
<bt:Image id="Icon.80x80" DefaultValue="https://localhost:3000/assets/icon-80.png"/>
</bt:Images>
<bt:Urls>
<bt:Url id="Commands.Url" DefaultValue="https://localhost:3000/commands.html"/>
<bt:Url id="Taskpane.Url" DefaultValue="https://localhost:3000/taskpane.html"/>
</bt:Urls>
<bt:ShortStrings>
<bt:String id="GroupLabel" DefaultValue="Contoso Add-in"/>
<bt:String id="TaskpaneButton.Label" DefaultValue="Show Taskpane"/>
<bt:String id="ActionButton.Label" DefaultValue="Perform an action"/>
</bt:ShortStrings>
<bt:LongStrings>
<bt:String id="TaskpaneButton.Tooltip" DefaultValue="Opens a pane displaying all available properties."/>
<bt:String id="ActionButton.Tooltip" DefaultValue="Perform an action when clicked."/>
</bt:LongStrings>
</Resources>
</VersionOverrides>
</OfficeApp>

Answer 1

ItemHasRegularExpressionMatch is only available on the Read command surface.
Please refer to the documentation here : https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/activation-rules#specify-activation-rules-in-a-manifest

Answer 2

should detect certain words when a user is composing messages
You can specify regular expression rules to have a contextual add-in activated when a match is found in specific fields of the message. Contextual add-ins activate only in read mode. Outlook doesn't activate contextual add-ins when the user is composing an item. There are also other scenarios where Outlook doesn't activate add-ins, for example, digitally signed items. For more information, see Activation rules for Outlook add-ins.