As Denis said: 4.0.0-RC3 stands for Release Candidate. It is not yet considered stable. You should not use a release candidate for production work.
I have a research. I need to reach the data and ı cant sign in.
So based on this, I assume that you have created a survey in 4.0 (unstable) and you have started a survey and it all worked fine. Then it stopped working? Or are you still in the starting phase?
What is strange is that it works with the other setup, so I assume that there is a problem with this specific database.
I would install the latest 3.x version and see if that works.
And again: NEVER use an unstable version of ANY software for production.