Telecharger steam like
I think you are right. You may need to recreate your test Sheet with a free, consumer account in order for us to see it.
Just from syntax and without being able to test it, it looks like there may be too many "where" statements:
=query('steam sales graph'!A:E,"select A, sum(E) where (A is not null and E > 0 and dateDiff(A,A)<7) group by A ")
Unfortunately, dateDiff(A,A) will always equal 0 because it is finding the difference between two instances of the same date.
If you can make a test sheet with a shareable link, feel free to post a new thread so more people see your new question.