Having problem with table name that contains dot like Staff.Users

I have a table name Staff.Users, and I have tried with TableRegistry::get(“Staff.Users”) but seens not working and I don’t know how to solve this problem. Can someone help? Thanks,

Dot notation is used for Plugins in CakePHP so there is conflict with it.
You should name your Model to follow conventions (for example Users) and then specify table you used (Staff.Users)
Here is explained how to use TableRegistry::get and specifying other parameters:
https://book.cakephp.org/3.0/en/orm/table-objects.html#configuring-table-objects