Hi,
Usually problem is with compress module. In web.config try to look for HttpCompress section and if it's turned on exclude video mime types in config
<
HttpCompress
turnedOn
=
"true"
defaultProvider
=
"Deflate"
useCaching
=
"true"
>
...
<
ExcludedMimeTypes
>
...
<
add
name
=
"mp4"
type
=
"video/mp4"
/>
<
add
name
=
"ogv"
type
=
"video/ogg"
/>
<
add
name
=
"webm"
type
=
"video/webm"
/>
...
</
ExcludedMimeTypes
>
</
HttpCompress
>
Next you need to check video format of your video, different browsers support different formats, to tackle this you will need to have same video in different format and set all of them as a source this way each browser will find one that it can play.
If you will still have trouble with playing video, I'll need more details about problems you are having.