Receiving a low AAV titer can be frustrating, especially after investing time in packaging and purification. The most common culprits include poor plasmid quality, suboptimal transfection efficiency, incorrect harvest timing, and degradation during purification. This article walks through each possible cause in detail, providing troubleshooting tips and quality control checkpoints. We also discuss the importance of using validated protocols and how to interpret titer measurement results from qPCR or ddPCR. By systematically ruling out these issues, researchers can improve their titer yields and ensure consistent vector production.