cant login into gui any more - rhel 7.5
 

I have installed rhel 7.5 about 10 days ago for our dev team.
I choose the "server with gui" and spent few hours configuring it as needed.
On the server(Dell t410) i have installed win2012 r2 first and then the rhel in order to have multi boot server which worked perfectlly.
On Thursday our dev team copied their work to the server and and i haves installed odbc client for sql server.
The server was rebooted few times and everything was ok.
I shutdown the server on Thursday and when i powered it up today, it doesnt boot into gui - i get the 7 logo and the little circle middle bottom that shows me that the os is loading but few seconds after it disappear the machine shows blank screen and the display goes into power save mode.
Pressing alt+ctrl+delete boot the machine to the same status.
trying to use the rescue option from the multi boot menu gets me the same result.
Windows is loading ok with no problem.
What went wrong?
Thanks in advance for any help.

One presumes that if you are installing RHEL, you have a license and support. What does RHEL support say about this?

You can always boot to RHEL, drop to a console, and check the log files and dmesg report for errors. There should be a big fat clue there.

Thanks for your reply.
I am (very) new to linux world - have lots of experience with windows.

I have for now the free month license and i opened a discussion here :
https://access.redhat.com/discussions/5281451
Do i need to open a case?

You mentioned that i need to "boot to RHEL, drop to a console" - my problem is that after choosing rhel in the boot menu, it goes to
rhel 7 boot screen, showing the 7 logo screen and after few seconds the display goes to power save mode and i can only alt+ctrl+del
the server.
How can i get to console?

update : i managed to get into console(using alt+ctrl+f2), user login was requested and while i was typing my login the screen goes blank and went into power save as before.
I switched displays to verify it is not display hardware problem and it happened in another display as well.
As before windows boot working fine - no display or any problems at all.
update 2 : i tried using the rescue option from the rhel install media. after getting into the last menu(where i can choose between mounting my system to a folder as is or in read only mode), i toggled around
the logs there and in every one of them after a while i get "pane is dead".