Problem with Joomla 3.4.8 and 3.5

[roxy39]

Hello,
I installed windows xampp 3.1.0 on my pc address F: \ xampp. Apache ports 80 and 443, the MySQL port is 3306.
I use it to expand my website with Joomla 3.4.8. which is in the file "htdocs". Everything works fine.
Wanting to test Joomla 3.5, I made an installation of the Beta2 and created a new site" essai35" that is in the same "htdocs" folder.
I can open the new site in frontend. But I can not get in backend. When I ask localhost/essai35/administrator, I have nothing, not even an error message.
How to solve this problem ?
Thank you for your advice

[Nobbie]

How to solve this problem ?

I dont know Joomla. I would ask in a Joomla Forum.