It seems you have turned on the stream aliasing functionality on. Stream names are not accessible when stream aliasing is on.
If you still wish to use the stream aliasing functionality, then you can use the addStreamAlias API to provide an alias name for the stream. Instead of accessing the stream with rtmp://<ip>/live/<streamname>, use rtmp://<ip>/live/<aliasName>. Alias names can only be played once. You can see detailed explanation about stream aliases in the User Guide.
If you do not want to use stream aliasing, you can disable it in the config.lua. Set hasStreamAliases to false.