Bluno USB Programming Trouble

Hi,

I've been having trouble programming a Bluno v2.0 board over USB

The card initially worked fine until I attempted to use the example program Hello_World for bluetooth comms.

The program initially compiled and ran but now i cannot re-program the Bluno card from the Arduino IDE.

Any program in the IDE compiles and then the upload fails with an error message: 

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xe9
Failed uploading: uploading error: exit status 1

I'm running Arduino IDE 2.3.2
Windows tells me the drivers for the USB port are up to date [Arduino LLC v1.2.3]

I've tried combinations of the Reset and Boot buttons and nothing seems to make any difference.

I also have 2 students using a DFRobot Bluno V2.0 who initially reported this error to me for their project work.

Is there a fix for this? or is the Bluno a ‘program once’ device?

regards

Dave Langstaff