The initialize error indicates that the device and programmer cannot communicate at all.
This is normally the case when there is a problem with the connection, or when the device does not operate.
Please check the following points.
The connection on p.290 of the user's manual is the signal connection during normal write.
For on-board programming, the power supply and clock are supplied on the board, and no clock is supplied from the programmer.
Moreover, at this time, set the TARGET VDD SWITCH of the FL-PR3 to the IN side.
In addition, switch the device's VPP and reset to the FL-PR3 during programming.
In this status, signals other than CLK should be connected as described in the manual and, if there is no problem with the clock oscillation, programming should be possible.