[Old and Slow]

I assume that you have the latest stable versions of MM and SM and any related plugins.

Try using a server start command like this:
srcds -console -condebug -port 27015 -norestart -game csgo +game_type 0 +game_mode 1 +map de_dust

The console and debug arguments will generate an extra log file in the csgo directory that may be helpful.

Start by adding pieces and not all at once.
First, plain server with just MM loaded (hide the VCF for SM so that it isn't processed)
With just MM, you should be able to try these commands in the server console:
meta version
meta list

The second one should not show anything yet if you have hidden the VCF file for SM.

Next enable just SM without any extra plugins.
Try these in the server console:
meta list (you should see some SM plugins)
sm version
sm plugins

Those should generate some text and SM has some default plugins.

If anything doesn't work look for the console.log file in the csgo directory.

At each point, see if the server works normally just with MM and SM loaded.

Finally, enable the BFG Warmod - I am not familiar with that, I assume it is a plugin.

Check the same command as above, you may find that something is not loading.

Anyway, good luck!