All right, try placing the MCP very near to the front panel of the Beomaster, as there could be a problem that reduces the range.
If it still doesn't work, I suspect that your Beomaster has been connected to a Beovision earlier and was programmed to Option 0, which means that it won't respond to IR commands. The bad part is that I don't think there's any way to reprogram it with the MCP - you would need to get your hands to a Beolink 1000 or a Beo4, at least for the time of the programming.