Flowplayer won’t play in Firefox

Error mesages on the page:
This page uses the non standard property “zoom”. Consider using calc() in the relevant property values, or using “transform” along with “transform-origin: 0 0”. carboniferous-limestone
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/wp…_v1.0.1/library/views/scripts/fonts/Amaranth-webfont.font.js” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/jquery.fancybox.pack.js?v=2.1.4” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-thumbs.js?v=1.0.7” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/wp…_v1.0.1/library/views/scripts/fonts/Amaranth-webfont.font.js” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
Loading failed for the <script> with source “https://www.history-of-wales-in-stone.gardenofwales.org.uk/wp…_v1.0.1/library/views/scripts/fonts/Amaranth-webfont.font.js”. carboniferous-limestone:52:1
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-buttons.js?v=1.0.5” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-media.js?v=1.0.5” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/jquery.fancybox.pack.js?v=2.1.4” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
Loading failed for the <script> with source “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/jquery.fancybox.pack.js?v=2.1.4”. carboniferous-limestone:163:1
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-buttons.js?v=1.0.5” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
Loading failed for the <script> with source “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-buttons.js?v=1.0.5”. carboniferous-limestone:173:1
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-media.js?v=1.0.5” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
Loading failed for the <script> with source “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-media.js?v=1.0.5”. carboniferous-limestone:174:1
The script from “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-thumbs.js?v=1.0.7” was loaded even though its MIME type (“text/html”) is not a valid JavaScript MIME type.
carboniferous-limestone
Loading failed for the <script> with source “https://www.history-of-wales-in-stone.gardenofwales.org.uk/fancybox/source/helpers/jquery.fancybox-thumbs.js?v=1.0.7”. carboniferous-limestone:177:1
TypeError: $(…).fancybox is not a function
carboniferous-limestone:167:18

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Oddly, in WordPress > Customise > Appearance > Site Identity Flowplayer DOES play. But not on the public side of the site. Why is this?