Cannot upload sketch - not in sync

I have been uploading different sketches to the NyBoard v1.1 so I can use different I2C devices with it. At one point, I started getting an error and it does not allow me to upload any new sketches, always with the same type of error. Below I am simply trying to upload a blank sketch:

Sketch uses 3852 bytes (11%) of program storage space. Maximum is 32256 bytes.
Global variables use 578 bytes (28%) of dynamic memory, leaving 1470 bytes for local variables. Maximum is 2048 bytes.
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x49
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x6e
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x69
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x74
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x20
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x73
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x65
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x72
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x76
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x6f
Failed uploading: uploading error: exit status 1

Any ideas?

Edit:

There is data coming from the serial console from a previous sketch, so the ATMega is still working:

09:47:57.058 -> Init servos: k 
09:47:57.192 -> Init IMU 
09:47:57.678 -> Init servos: k 
09:47:57.810 -> Init IMU 
09:47:58.309 -> Init servos: k 
09:47:58.417 -> Init IMU 
09:47:58.960 -> Init servos: k