I don’t believe the snap image has been updated for several years. Exercism doesn’t reference it anymore at least. Did you first download the exercise through exercism download? My gut says perhaps your token is misconfigured. If you do exercism configure is there a < at the beginning or end of the token (don’t paste your token here)?
It looks like you’re running an old version of the CLI. Consider updating it.
You may need to force download (which will delete your code, so save a copy). If you cd into the correct directory, you should be able to paste your code then run exercism submit without needing to specify filenames.
The exercism tool requires, for submitting, the presence of the file ./.exercism/metadata.json under the current directory. You have to be in the exercise’s download directory to submit.
Version 3.0.13 was released in October 2019. There have been substantial changes to the server in the past 5 years, so I’m not surprised there are API errors.
I’d strongly recommend getting the exercism tool from Homebrew.
My recommendation is to download the correct executable directly and install it in “user space”. The updates happen restricted to the executable itself, and tends to go smoothly, without relying on a package manager.