While I cannot possibly know why you cannot focus on anything, I might suggest a solution. I have a major problem (!) with time management, I am consistently unable to do what I want to do or what I need to do. It is frustrating.
One of the suggestions is to "Let it all go" and not to think that you have to focus. The more you concentrate on the word "focus", the less you are able to do it.
Another suggestion, that worked for me - keep a diary and write in a free-floating manner. No need to organize your thoughts - just simple "put pen to paper" and produce three pages every day, even if the only thing you can write is "I cannot write. I cannot write. I cannot write. ...."
Give yourself smaller tasks, but complete them. Or make records, how much you can accomplish before you lose your focus or concentration.
In any case, before you or somebody else can come up with the strategy to solve your problem, you have to gather enough data to describe your problem (or opportunity).
As ironic as it sounds you need to focus in order to solve your "focus" problem. I am sure you will be fine.
All the best,