I have properly located the unloader such that it is aligned with the cargo train car, however it doesn't automatically move the contents from the cargo to the unloader inventory. Is there something I am doing wrong?

What are you trying to unload? BRLs only handle ore and such unless you change the setting.

I've been running into a simular issue. I've got 4 Bulk Rail Loaders in a row;
1 Iron Pipe
2 Iron Gear
3 Steel Plate
4 Solid Fuel

Unit 1, 2 and 4 work perfect but unit 3 (steel plate) refuses to load into the rail cargo wagon.
Strangely enough, I can put Iron Gears, Iron Pipe and Solid fuel into unit 3 and it won't load those either. Plastic Bars do get loaded though.

I suspect the mod 'Larger Stack Size' (https://mods.factorio.com/mod/Larger%20stack%20Size) may have something to do with this, I've got two different versions of the 'Steel-Plate'.

Can you post a save I can look at?

I've figured it out, took some digging though! I stumbled across a post that mentions a mod-configuration menu (ingame press ESC -> Settings -> Mod Settings). Going into tab 'Map' and to the Bulk Rail Loader settings and changed 'Allowed Items from 'Ore' to 'Any'. This fixed my issue.

By default Bulk Rail Loader is set to 'Ore' only but it works for a lot of non-ore materials. If it had been bulk-loading and unloading only Ore, the issue would have been a bit more obvious

It should not be loading any of the 4 item types you listed on the default (Ore) setting.

This is all spelled out in detail under the “What items are supported?” heading of the documentation.