It could be an issue with the codecs (browsers are usually pretty limited in what they support). You could try to use a client like Jellyfin Media Player instead. It bundles libmpv, so it plays almost any video format there is.

You should put some quotes where you use the array:

not_what_you_think=( "a b" "c" "d" )
for sneaky in "${not_what_you_think[@]}"; do
  echo "This is sneaky: ${sneaky}"
done

This is sneaky: a b
This is sneaky: c
This is sneaky: d