Side-loaded Outlook addin not showing up on mobile

Question

I've been developing an Outlook add-in. It works fine on desktop and web, but now I've added the mobile section to the manifest... everything still works on desktop and web... but nothing show's up in the apps section on mobile... I submitted the manifest to Microsoft and even they noted it wasn't showing... while providing no helpful information on why it wasn't showing... and there's no debugging tools I can see to test why it isn't working.

The FormFactor is in the 1.1 override and after the desktop formfactor. I'm testing with O365 accounts, not on-prem exchange.

        <VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides/1.1" xsi:type="VersionOverridesV1_1">
            <Requirements>
                <bt:Sets DefaultMinVersion="1.13">
                    <bt:Set Name="Mailbox" />
                </bt:Sets>
            </Requirements>

            <Hosts>
                <Host xsi:type="MailHost">
                    <DesktopFormFactor>
...
                    </DesktopFormFactor>
                    <MobileFormFactor>
                        <!-- Message Read -->
                        <ExtensionPoint xsi:type="MobileMessageReadCommandSurface">
                            <!-- Only one group for mobile -->
                            <Group id="mobileMessageReadGroup">
                                <Label resid="groupLabel" />
                                <!-- Launch the add-in : task pane button -->
                                <Control xsi:type="MobileButton" id="mobileMessageReadOpenToggle">
                                    <Label resid="messageReadOpenToggleLabel" />
                                    <Icon>
                                        <bt:Image size="25" scale="1"  resid="classify-icon-25" />
                                        <bt:Image size="25" scale="2"  resid="classify-icon-50" />
                                        <bt:Image size="25" scale="3"  resid="classify-icon-75" />
                                        <bt:Image size="32" scale="1"  resid="classify-icon-32" />
                                        <bt:Image size="32" scale="2"  resid="classify-icon-64" />
                                        <bt:Image size="32" scale="3"  resid="classify-icon-96" />
                                        <bt:Image size="48" scale="1"  resid="classify-icon-48" />
                                        <bt:Image size="48" scale="2"  resid="classify-icon-96" />
                                        <bt:Image size="48" scale="3"  resid="classify-icon-144" />
                                    </Icon>
                                    <Action xsi:type="ShowTaskpane">
                                        <SourceLocation resid="messageReadTaskPaneUrl" />
                                        <!--
                                        <SupportsPinning>true</SupportsPinning>
                                        -->
                                    </Action>
                                </Control>
                            </Group>
                        </ExtensionPoint>
                    </MobileFormFactor>
                </Host>
            </Hosts>