Expansion Arrows Does Not Appear

[Guille]

Hello! I have created a tree for a project that I'm doing but I cannot get the expansion arrows to appear when the web page is loaded. When I go to the web page and click on a folder that has subfolders, then the expand arrows appear. I can't find a solution. I hope you can help me, please. All the best!!

 

After loading the web page:                                                                                 After clicking the parent folder:

                                                    

 

 

[Guille]

Solved!