Outlook add-in command not showing in Outlook 2016 ribbon - outlook

Question

I have been converting the manifest for my Outlook add-in to use a add-in command to show an icon in the ribbon if the user is on Outlook 2016. Unfortunately, I can't seem to get an icon to show up in the ribbon.
The add-in works fine on other clients.
Here is an anonymized version the manifest file I am using:
<?xml version="1.0" encoding="utf-8"?>
<OfficeApp xsi:type="MailApp"
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">
<Id>892bf749-7601-428e-a658-1d32b883a712</Id>
<Version>1.0.0</Version>
<ProviderName>My Name</ProviderName>
<DefaultLocale>en-US</DefaultLocale>
<DisplayName DefaultValue="My Addin" />
<Description DefaultValue="Description goes here." />
<IconUrl DefaultValue="https://myaddin-host.com/icon.png" />
<HighResolutionIconUrl DefaultValue="https://myaddin-host.com/icon.png" />
<SupportUrl DefaultValue="http://www.sydience.com/?page_id=7" />
<Hosts>
<Host Name="Mailbox" />
</Hosts>
<Requirements>
<Sets>
<Set Name="MailBox" MinVersion="1.1" />
</Sets>
</Requirements>
<FormSettings>
<Form xsi:type="ItemRead">
<DesktopSettings>
<SourceLocation DefaultValue="https://myaddin-host.com/v1.1/AppRead/Home/Home.html" />
<RequestedHeight>350</RequestedHeight>
</DesktopSettings>
<TabletSettings>
<SourceLocation DefaultValue="https://myaddin-host.com/v1.1/AppRead/Home/Home.html" />
<RequestedHeight>350</RequestedHeight>
</TabletSettings>
<PhoneSettings>
<SourceLocation DefaultValue="https://myaddin-host.com/v1.1/AppRead/Home/Home.html" />
</PhoneSettings>
</Form>
</FormSettings>
<Permissions>ReadWriteItem</Permissions>
<Rule xsi:type="RuleCollection" Mode="And">
<Rule xsi:type="ItemIs" ItemType="Message" FormType="Read" />
</Rule>
<VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides" xsi:type="VersionOverridesV1_0">
<Description resid="residDescription" />
<Requirements>
<bt:Sets DefaultMinVersion="1.3">
<bt:Set Name="Mailbox" />
</bt:Sets>
</Requirements>
<Hosts>
<Host xsi:type="MailHost">
<DesktopFormFactor>
<ExtensionPoint xsi:type="MessageReadCommandSurface">
<OfficeTab id="TabDefault">
<Group id="msgReadMyAddinGroup">
<Label resid="groupLabel" />
<Control xsi:type="Button" id="msgReadOpenPaneButton">
<Label resid="paneReadButtonLabel" />
<Tooltip resid="paneReadTipTitle" />
<Supertip>
<Title resid="paneReadSuperTipTitle" />
<Description resid="paneReadSuperTipDescription" />
</Supertip>
<Icon>
<bt:Image size="16" resid="myaddin-icon-16" />
<bt:Image size="32" resid="myaddin-icon-32" />
<bt:Image size="80" resid="myaddin-icon-80" />
</Icon>
<Action xsi:type="ShowTaskpane">
<SourceLocation resid="readTaskPaneUrl" />
</Action>
</Control>
</Group>
</OfficeTab>
</ExtensionPoint>
</DesktopFormFactor>
</Host>
</Hosts>
<Resources>
<bt:Images>
<bt:Image id="myaddin-icon-16" DefaultValue="https://myaddin-host.com/v1.1/Images/myaddin-icon-16.png" />
<bt:Image id="myaddin-icon-32" DefaultValue="https://myaddin-host.com/v1.1/Images/myaddin-icon-32.png" />
<bt:Image id="myaddin-icon-80" DefaultValue="https://myaddin-host.com/v1.1/Images/myaddin-icon-80.png" />
</bt:Images>
<bt:Urls>
<bt:Url id="readTaskPaneUrl" DefaultValue="https://myaddin-host.com/v1.1/AppRead/Home/Home.html" />
</bt:Urls>
<bt:ShortStrings>
<bt:String id="residDescription" DefaultValue="My Outlook add-in" />
<bt:String id="groupLabel" DefaultValue="My Addin" />
<bt:String id="paneReadButtonLabel" DefaultValue="Show Pan" />
<bt:String id="paneReadTipTitle" DefaultValue="More text here" />
<bt:String id="paneReadSuperTipTitle" DefaultValue="More text here" />
<bt:String id="paneReadSuperTipDescription" DefaultValue="More text here" />
</bt:ShortStrings>
</Resources>
</VersionOverrides>
</OfficeApp>

Answer 1

Your bt:String resources for the Tooltip and Description elements have to be in the bt:LongStrings element. Try replacing:
<bt:ShortStrings>
<bt:String id="residDescription" DefaultValue="My Outlook add-in" />
<bt:String id="groupLabel" DefaultValue="My Addin" />
<bt:String id="paneReadButtonLabel" DefaultValue="Show Pan" />
<bt:String id="paneReadTipTitle" DefaultValue="More text here" />
<bt:String id="paneReadSuperTipTitle" DefaultValue="More text here" />
<bt:String id="paneReadSuperTipDescription" DefaultValue="More text here" />
</bt:ShortStrings>
With:
<bt:ShortStrings>
<bt:String id="residDescription" DefaultValue="My Outlook add-in" />
<bt:String id="groupLabel" DefaultValue="My Addin" />
<bt:String id="paneReadButtonLabel" DefaultValue="Show Pan" />
<bt:String id="paneReadSuperTipTitle" DefaultValue="More text here" />
</bt:ShortStrings>
<bt:LongStrings>
<bt:String id="paneReadTipTitle" DefaultValue="More text here" />
<bt:String id="paneReadSuperTipDescription" DefaultValue="More text here" />
</bt:LongStrings>