The sentence is ungrammatical because of the presence of "ever". "Ever" belongs to a group of words called "negative polarity items".
The unusual thing about negative polarity items is that they can only appear when there is some suggestion of doubt or unreality in the sentence.
Here are a few of the situations where you can use "ever":
- In an explicitly negative sentence. Note that "ever" becomes "never" when negated.
I have never done that.
- In an implicitly negative sentence, such as one expressing doubt or infrequency.
I hardly ever do that.
I doubt that I've ever done that.
- In a question (because the answer could be "no"!).
Have you ever done that?
- In a hypothetical situation.
If you ever do this, let me know.
There are a couple of other situations. See this answer on English Language & Usage for more detail.
Another negative polarity item that often causes difficulty is "any".