the Midsummer Cawnival does not activated (dedicated server)

Please try running the following commands in the console (press ~ to open the console)

print(c_findnext("carnival_host").Transform:GetPosition())    
print(TheWorld.components.carnivalevent)

If you are running with caves enabled, please make sure it says Remote beside the console input box. Press Ctrl to toggle it on if needed.
The commands will print to the server's log files.
 

Now please attach your log files
\Documents\Klei\DoNotStarveTogether\client_log.txt
\Documents\Klei\DoNotStarveTogether\<your steam id>\Cluster_#\Master\server_log.txt

replace Cluster_# with the correct folder for this world or you can click on the folder icon in the host game world select screen to get there.