Elgg 5.0.0. - Beta 1 Testing on my own xampp

I enjoyed the new version of Elgg, especial the new layout for administrators. It is realyy a good ide to use dropdown menus to classify the facilities on top bar. And of  the use of Php 8x is another new option. Conratulations the staff. 

I have installed the new version on my own xampp server on my computer. The installation is completed without any errors. I created a new user prorperly. Everything went ok.

I tried to create a blog including a picture it displayed it on the ckeditor page, but the "Couldn't upload file: 20170415130736-008193b0.jpg" error displayed. So It wasn't saved.

To sum up, it is ok when you create a blog in text, but it produces an error if it has a picture. Any idea?