Can't join session

Hi all
I stuck for two days on this question,i trid both in C++ and Blueprint.I can create session,can find session and can join session also,but when i try to do ClientTravel,i will get this warning

LogOnline: Warning: OSS: Invalid session info for session Game in GetResolvedConnectString()

So what did i miss?Please help me,Thank you!

■■■■,when i bulit my project and run the exe,it work well…