Is it definitely a Beomaster 5000 that you have, and definitely an MCP5000? They will only work with each other, and the BM5500/MCP5000 or BM5000/MCP5500 combo will not work. If they are compatible, try turning on a video camera on a mobile phone and press one of the buttons on the MCP. You should be able to see the IR transmission, and also if it's working the transmission from the BM 5000 too.
President, Beomaster 8000 Appreciation Society