I downloaded the test video and it played perfectly, although my own presentation was still refusing to play my video (also a wmv) on the same computer. I added my video to testvideo.odp and it played in that, so added my other material and got the slideshow that I had been struggling with for a fortnight to work in testvideo.odp. It is a little bit flaky and doesn’t like me meddling with the transitions, but it goes. I’ve no idea why, but thank you.
You are welcome 
Sadly Impress is so flakey with this I have gone back to PowerPoint. I must be sure that things will run in a presentation,
You might like to see the release notes for LibreOffice 26.2, ReleaseNotes/26.2 - The Document Foundation Wiki
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