Video not showing thumbnail on mobile devices

I have some self-hosted videos on my blog that show and play normally on PC browsers but on mobiles (doesn’t matter what browser) though they play normally they don’t show the thumbnail, so it’s just a blank white space with a grey and white ‘play’ symbol in the middle where the video should be.

And by thumbnail I mean the standard video thumbnail, not an added poster image.

An example of the block code is this:

<figure class=”wp-block-video”><video controls=”” src=”https://tiptonscroft.org.uk/blog/wp-content/uploads/2020/05/2020.05.21-Hootycam-A.mov”></video></figure&gt;

Help appreciated!

The page I need help with: [log in to see the link]