I'm assuming this is BVN404?

As a start, look your web.config on Integration and confirm you can see a <bvn404handler> section and reference to bvn404 in the protectedmodules section.

You could also check access is restricted to the gadget in the web.config, look for securedcomponents section and see if there's a reference to bvnetwork there. It may have a role against it meaning you can only see the gadget if you have the assigned role.

The handler is on integration. I didn't see anything for securedcomponents. But I did see a section under protectedmodules. I found this:

<episerver.shell>
    <publicModules rootPath="~/modules/" autoDiscovery="Modules" />
    <protectedModules rootPath="~/EPiServer/">
        <add name="BVNetwork.404Handler" />

and this:

<virtualPathProviders>
    <clear />
    <add name="ProtectedModules" virtualPath="~/EPiServer/" physicalPath="Modules\_Protected" type="EPiServer.Web.Hosting.VirtualPathNonUnifiedProvider, EPiServer.Framework.AspNet" />
</virtualPathProviders>

and this:

<location path="Modules/_Protected">
    <system.webServer>
        <validation validateIntegratedModeConfiguration="false" />
        <handlers>
            <clear />
            <add name="BlockDirectAccessToProtectedModules" path="*" verb="*" preCondition="integratedMode" type="System.Web.HttpNotFoundHandler" />
        </handlers>
    </system.webServer>
</location>

Do I need to set specific permissions or something? This was supposedly working before. So it's weird that it's not now.

Try adding this in:

<episerver.shell>
        <viewManager>
            <securedComponents>
                <add definitionName="BVNetwork.NotFound.Controllers.NotFoundRedirectController" allowedRoles="Administrators" />
            </securedComponents>
        </viewManager>

I added it, but it did not seem to work. I used Administrators and CmsAdmins, which is what my security section shows for the admin role. I restarted the app after each change and it still does not appear. This is what my episerver.shell section looks like on integration. It's odd that it works in local dev, but not on the website in integration.

Couple more things for you to check

1. You have this in your integration web.config: <bvn404Handler handlerMode="On">

2. In your web folder under modules/_protected that the bvn404 folder exists and the correct files are there. Compare it to your local env.

Ah. That second item is the problem, I think. The integration environment doens't have the BVN404 zip file. But local does.

Integration:

Local:

I need to figure out why all of the zips made it to their folders, but this one didn't.