If your DigiSpark is no longer getting programmed from the Arduino IDE, when plugging it in, you might have to re-program the Micronucleus bootloader. You can do this using the Raspberry Pi if you do not have an AVR programmer.

Preperation

Install the AVRDUDE programmer on the Raspberry Pi:

apt-get install avrdude

Copy the default AVRDUDE configuration file to your home directory.

cp /etc/avrdude.conf ~/avrdude_gpio.conf
nano ~/avrdude_gpio.conf

Add this to the end of the file to make AVRDUDE use the Raspberry Pi GPIO port as programming port.

# Raspberry PI GPIO configuration for avrdude.
# Change the lines below to the GPIO pins connected to the AVR.
programmer
  id    = "rpi";
  desc  = "Use the Linux sysfs interface to bitbang GPIO lines";
  type  = "linuxgpio";
  reset = 12;
  sck   = 24;
  mosi  = 23;
  miso  = 18;
;

Next, download the Micronucleus bootloader file called micronucleus-1.06.hex.

wget https://github.com/micronucleus/micronucleus/raw/80419704f68bf0783c5de63a6a4b9d89b45235c7/firmware/releases/micronucleus-1.06.hex

Connect the DigiSpark to the Raspberry Pi using the table below.

When the DigiSpark is connected run this command from your home directory to program the AVR with the bootloader.

sudo avrdude -p attiny85 -C avrdude_gpio.conf -c rpi -U flash:w:micronucleus-1.06.hex:i -U lfuse:w:0xF1:m -U hfuse:w:0x5F:m

AVRDUDE should respond something like this:

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e930b
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "micronucleus-1.06.hex"
avrdude: writing flash (8162 bytes):

Writing | ################################################## | 100% 1.28s

avrdude: 8162 bytes of flash written
avrdude: verifying flash memory against micronucleus-1.06.hex:
avrdude: load data flash data from input file micronucleus-1.06.hex:
avrdude: input file micronucleus-1.06.hex contains 8162 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 1.09s

avrdude: verifying ...
avrdude: 8162 bytes of flash verified
avrdude: reading input file "0xF1"
avrdude: writing lfuse (1 bytes):

Writing | ################################################## | 100% 0.00s

avrdude: 1 bytes of lfuse written
avrdude: verifying lfuse memory against 0xF1:
avrdude: load data lfuse data from input file 0xF1:
avrdude: input file 0xF1 contains 1 bytes
avrdude: reading on-chip lfuse data:

Reading | ################################################## | 100% 0.00s

avrdude: verifying ...
avrdude: 1 bytes of lfuse verified
avrdude: reading input file "0x5F"
avrdude: writing hfuse (1 bytes):

Writing | ################################################## | 100% 0.01s

avrdude: 1 bytes of hfuse written
avrdude: verifying hfuse memory against 0x5F:
avrdude: load data hfuse data from input file 0x5F:
avrdude: input file 0x5F contains 1 bytes
avrdude: reading on-chip hfuse data:

Reading | ################################################## | 100% 0.00s

avrdude: verifying ...
avrdude: 1 bytes of hfuse verified

avrdude: safemode: Fuses OK (E:FE, H:5F, L:F1)

avrdude done.  Thank you.

After which the Arduino IDE should be able to program it again.