Welcome back, @Hajar!
This looks a lot like an error message we've run into before. Take a look at this post, and let us know if it helps.
Incidentally, 2019.4 is almost a year and a half old now. It's using the same Python version as 2020.8, so I don't expect updating will solve your problem, but installing a new version will get you some newer features and better performance in a couple places.
Best of luck,
Chris 