Rstudio server login problem

I just finished installing Rstudio on Red Hat Linux server. and I can access Rstudio server through [server ip]:8787.
I tried to log in, but there are some problems.
I have two accounts on linux server, but both account failed to log in.
when I tried to log in with the first account, it throws a message on the login page stating Rstudio initiallization Error : Unable to connect to service.
In the case of the second account, the server said that it is an Unauthorized user.
Is there anyone who solves this login problem?