No interest earned for 4 months on large investment in Old Mutual Money Market Unit Trust Fund

<p>My son inherited a large sum of money from his grandfather.We decided to put in into the Old Mutual Unit Trust Fund as in this volatile market it seemed the lowest risk.However to date no interest has been received and the amount in the 4 months remains unchanged.Where is the interest?????</p> <p>Why invest if your investment does not grow????</p>