[FTC]: Failed to start robot

[mikets]

The robot controller phone keep giving me the following message:
Robot Status: failed to start robot
Unable to open Modern Robotics USB DC Motor Controller
Unable to open USB device AL00YC5V - FT232R USB UART [AL00YC5V]: Unable to open USB device with serial number AL00YC5V

I had to keep doing a "Setting->Restart Robot". If I am lucky, I will be able to succeed in 4 attempts. Sometimes, it helps if I power cycle the USB core interface. But then when trying to run the TeleOp opmode code, it went back to the above error. Lately, I am not able to get out of this. Please help.

BTW, if I try to create a new Robot Configuration profile, no matter how many times I pressed the "Scan" button, it still said it found no hardware. If you try long enough, it may find one or two modules but very difficult to get it to find all the connected modules.