Hello Fedora, Could you share the solution please?
Thanks in advance!

I will check!

Could it be that this is because I changed the default theme ?
When I insert an navbar the icons also disapear.
I think is something with the theme.
The only thing I did was to create a Theme from the default one and changed the colors. Nothing more.

Noup, I have not changed the icons. The javascript console shows that the app is trying to load some svg file.
Another thing is that some pages of the app show the icon correctly but when you open the page to edit it in the designer and save then the icon disapears.

Helo Ihor,
Is your answer related to the problem with the back button?¿
I already solved the css-style issues.
Thanks.

the name is "appclinica"

Evgene, Right now in my app the "back buttons" icons are not visible.
Could you access to my app and see if I'm having some kind of problems please?...
I activated the option to share with the support team.
Thanks again.

Thanks....
In case this could help to others, I managed to recover the whole file structure in color black . To do that the only step that worked was to delete the root directory of my project and then undo the changes.