Without the exact message and detailed info about the project, your version of AE, your system etc. nobody can tell you what to do.
Sorry I have version 126.96.36.199 and the exact message it says:
After Effects warning: a layer has missing dependencies.
Text Layer: Font family: "Minion Pro," Font style: "Medium It"
After Effects warning: Unable to create font.
Do you have that font installed on your system?