Why won't Amazon Prime play allow me to play movies and tv shows on Mac OS 10.14.3, but it shows me movie trailers on the same web browser (while it's telling me that I need to upgrade my OS). Obviously if it's able to show me trailers, then it should be able to show me the whole movie, right? The video from Amazon Prime DOES work, on Chrome, on Mac OS 10.14.3, so why is it refusing to play movies and videos?
Amazon Help – Prime Video System Requirements for Computers indicates that Amazon Prime Video for Mac is for Macs "Running macOS 11.4 Big Sur or Higher."
It looks like Amazon has decided to cut off support for Macs running older versions of macOS, like 10.14.* (Mojave). You could ask Amazon "why" they decided to cut you off – but it appears that if you get things to work on anything less than macOS 11.4, you should count yourself lucky that they work at all.
Amazon Help – Prime Video System Requirements for Computers indicates that Amazon Prime Video for Mac is for Macs "Running macOS 11.4 Big Sur or Higher."
It looks like Amazon has decided to cut off support for Macs running older versions of macOS, like 10.14.* (Mojave). You could ask Amazon "why" they decided to cut you off – but it appears that if you get things to work on anything less than macOS 11.4, you should count yourself lucky that they work at all.
likely amazons site use some components which rely a newer javascript engine than the web browser you attempt to use do not support, best you can do is to try other browsers, if it was me then my first try would be firefox they are suppose to be ok at giving newer support for older operating systems
you can also test opera and or brave to see if they have versions that support your operating system and newer browser features
if non of the browsers work then you're pretty much stuck.
Developers that build macOS compatible applications have control over what older version of macOS is supported by the app. The current version of Amazon Prime video in the Mac App Store requires macOS Ventura (13.0) or later. That is why it is telling you to upgrade your operating system from Mojave.
Updating Mojave to 10.14.6 won't solve your issue here.
Amazon Prime Video playback issue on macOS 10.14.3
