MSSQL_REPL-2147199360 Unable to decide if MakeGeneration is needed.

Error messages: 
Unable to decide if MakeGeneration is needed. (Source: MSSQL_REPL, Error number: MSSQL_REPL-2147199360) 
Get help: http://help/MSSQL_REPL-2147199360 
Query timeout expired (Source: MSSQLServer, Error number: 0) 
Get help: http://help/0 
The merge process failed to execute a query because the query timed out. If this failure continues, increase the query timeout for the process. When troubleshooting, restart the synchronization with verbose history logging and specify an output file to which to write. (Source: MSSQLServer, Error number: 0) 
Get help: http://help/0

If Merge Agent was not being blocked, see following ReplTalk BLOG posting for tips and techniques to correct this error.

Reducing Impact of Large Updates on Merge Replication