First see the main troubleshooting section

If your sketch uses DigiUSB to communicate with the PC, you need the legacy 0.1 version of libusb (http://www.libusb.org/). For compiling the DigiUSB programs, ensure the package libusb-compat-devel is installed.

Try running Arduino as root. If possible try the whole process as root.

If using Ubuntu or similar try the step below, if not make sure you have proper permission for the device.

Bad permissions generally cause the “Abort mission! -1 error has occurred …” error during upload. “micronucleus: library/micronucleus_lib.c:63: micronucleus_connect: Assertion `res >= 4' failed.” is also a result of bad permissions.

If you get java: not found, install a Java package, such as OpenJDK.

If you are running Ubuntu (and possible some other distros) and getting errors on upload or other strange results try this: (from: https://github.com/Bluebie/micronucleus-t85/wiki/Ubuntu-Linux)

Ubuntu and other modern Linux distibutions use udev to manage device files when USB devices are added and removed. By default, udev will create a device with read-only permission which will not allow to you download code. You must place the udev rules below into a file named /etc/udev/rules.d/49-micronucleus.rules

These rules are adapted from those used for Teensy boards, maintained [here](http://www.pjrc.com/teensy/49-teensy.rules)

# UDEV Rules for Micronucleus boards including the Digispark.
# This file must be placed at:
#
# /etc/udev/rules.d/49-micronucleus.rules    (preferred location)
#   or
# /lib/udev/rules.d/49-micronucleus.rules    (req'd on some broken systems)
#
# After this file is copied, physically unplug and reconnect the board.
#
SUBSYSTEMS=="usb", ATTRS{idVendor}=="16d0", ATTRS{idProduct}=="0753", MODE:="0666"
KERNEL=="ttyACM*", ATTRS{idVendor}=="16d0", ATTRS{idProduct}=="0753", MODE:="0666", ENV{ID_MM_DEVICE_IGNORE}="1"
#
# If you share your linux system with other users, or just don't like the
# idea of write permission for everybody, you can replace MODE:="0666" with
# OWNER:="yourusername" to create the device owned by you, or with
# GROUP:="somegroupname" and mange access using standard unix groups.