But during a test to get information for you I solved my issue: for some reasons, operator IN is case sensitive. But EQ is not. That's why I was getting different results.
When you mean "not getting anything", do you mean the api response is as such?
{
"total": 0,
"results": []
}
If you get a total 0, then the response is intended. If you have gotten any other error message, do share; it seems that your filter is correct, pretty much the same as what I used.
But during a test to get information for you I solved my issue: for some reasons, operator IN is case sensitive. But EQ is not. That's why I was getting different results.