Plugin doesn't work

[Traviata56]

When I publish or update a post it gives error message (see screenshot) and the post isn't posted to Medium. (see screenshot where the original box is still visible after publishing)

This happens since about 10 days on several WP sites with 2 different themes.
I have deleted and reinstalled the plugin, talked with support teams, no change.

I tried also the import tool of Medium, it doesn't seem to work for embedded videos in the post. (3 of 4 didn't work, all of them had videos embedded)

Can anyone who has the knowledge (which I definitely don't have) have a look into what happens and hopefully update the plugin?
Thanks
Heidi

[RocksteadyTC]

Fixed #133