Which flashing?

Slow Flash ... no rudder signal ...
Intermittent flash ... Alarm ... when power turned on in Rate/normal mode. gyro not initialized.
Double flash ... when rudder command from TX is not equal to memorized neutral signal of gyro. This is OK if you are moving the stick but should stop when no stick input is occuring. Also after gyro initialization/meorization, if you adjust the rudder trim, this will occur. You will need to reinitialize for the new neutral setting.
Single Flash ... occurs only when you are manually reinitializing the gyro via the rapid mode change method.

Like others said, Turn TX on first, set TX to HH/AVCS mode, then power on heli/gyro, then wait until the gyro LED goes steady. After that, if you adjust the TX rudder trim, you will need to reinitialize the gyro ... either power off/on method or the rapid mode change method.

Good Luck,
d.tipton