I ran the code that you posted with a single servo on channel 0 and it behaved as expected, ie sweeping back and forth
I used a powerbank as the power supply for the servos so there was 5V at the power connector, whilst the PCA9685 was powered from the Arduino Nano that I uploaded the code to and SDA/SCL were connected to the A4/A5 pins respectively
All in all, no surprises
Have you run the I2C scanner yet ?