Mason & Mason / DSM, Inc.
Thirteen years as the only developer for a right-of-way appraisal firm — an operating system built inside their Lotus Notes estate, then rebuilt twice as Microsoft discontinued the platform underneath it.
Microsoft ended Silverlight support on 12 October 2021. No current browser loads the plug-in. Every Silverlight line-of-business app is now either frozen on an old machine with an old browser, or being rewritten — and the rewrite is where things go wrong, because the people who knew what the app actually did have usually left.
I have shipped on Silverlight and I have migrated off it. The exit is usually a modern .NET web front end — Blazor or ASP.NET Core — over the same database, moved one screen at a time so the business keeps running on the old app until the new one has proved itself. Where the app was generated (LightSwitch, WCF RIA Services), I know what the generator produced, which is what makes the exit tractable rather than a rewrite from a blank page.
LightSwitch generated your app. Nobody can regenerate it now.
Your records are in Notes databases. Getting them out is the job.