Problem Retrieving references

When I search for a reference, it “confirms online search” and finds “records”. When I click OK button to retrieve… it stays blank… and never brings the reference down as it used to do. Thank to anyone who can help me sort this out.

Are you sure it isn’t a match to something you already retrieved once, (even if I clear the current “set”)?  I find that if it is in a current set, it won’t find it again (unless I change to search currently retrieved set) and it looks like it doesn’t work.