Roger,
Sorry I didn't reply sooner. I was enjoying some holidays with the missus.
I may not be able to fix your specific issue as I have not experienced a Trinket that gets stuck in read-only mode. Perhaps a file got corrupted. At any rate, I can help you erase the memory and reformat the filesystem so that you can reset and start all over again with a fresh board.
What makes the 'write-protect' turn on?
On the USB drive you will see (2) program files - boot.py and main.py. It's boot.py that loads first at power-up. That is where the code 'remounts' the memory and allows access by USB (holding the touch pin)(your computer will have read/write access) or by the main.py program (not holding the touch pin)(your computer will see it as write protected).
What can I do to make it work properly?
It may be simplest to erase everything and start over from scratch. This is not as hard as it sounds, it just involves some reading to learn about CircuitPython and how it works. Don't worry, playing with some code shouldn't permanently damage your Trinket (wrong wiring on the other hand...).
First you will need to install a simple code editing program on your computer. The program recommended by Adafruit is called Mu (don't ask me where they get these names from). The Adafruit tutorial that explains the installation is
https://learn.adafruit.com/welcome-to-circuitpython/installing-mu-editor Mu will allow you to open and edit the program code. It also has a 'serial console' - a window where you can interact with the micro-controller. You may have noticed some print statements in the program code. The serial console is where the printed statements appear. Error codes and statements will also show here.
For some information on connecting to the serial console read through
https://learn.adafruit.com/welcome-to-circuitpython/kattni-connecting-to-the-serial-console and
https://learn.adafruit.com/welcome-to-circuitpython/interacting-with-the-serial-console to get the idea. From the serial console you can interact directly with the microprocessor by entering the REPL mode. For information on the REPL see
https://learn.adafruit.com/welcome-to-circuitpython/the-replUsing the REPL you can enter a few lines of code to erase the memory. This will allow you to start fresh and reload CircuitPython and then the timer programs and libraries. Once you are connected and in the REPL mode you will see the >>> cursor. Type the following:
>>> import storage
>>> storage.erase_filesystem()
Hit enter and the CIRCUITPY drive will be erased and reformatted, and your board will restart. That's it!
Then follow my instructions using the downloaded files from my web page
https://circuitflyer.com to reprogram the Trinket. Don't forget to install CircuitPython first using the .UF2 file included in the download. PM me if you have any trouble.
Paul