Why can't I see the tasks on the board?

Question

Project management

Good afternoon.
We moved to a new project in fat, I want to make boards for each team.
I create for example an Android filter. Standard filter, but the performers are only Android developers to see only their tasks, and then the magic begins. I open this filter just in fat and see 10 tasks, then in the next tab, I create a board with the same filter, open it and there are zero tasks.
The tasks are open, the filter is simple and normal, it is indicated correctly on the board, I don’t understand what’s the matter, either the skis are not going, or I’m already swimming.
I sin that this project has a slightly different task structure and all improvements are carried out within the framework of business tasks, that is, a head task is created from the business, which is then divided into subtasks within this head task, on Android, ios and server. Is my assumption correct that subtasks are not visible on the boards? But that's dumb, no?
In short, guys, orient who the camel is.
Thanks