grid generation error

When I am about to generate the grid for this geometry shown below:
 
There is an error saying that "index in position 2 exceeds array bounds"

I wonder what is the cause of this error and how could I possibly fix it?

It is not possible to give any advice from your screenshots alone. Please first confirm that you are using the latest build of FEATool (currently v1.12.4 build 20.07.188):

https://github.com/precise-simulation/featool-multiphysics/releases

If not, please update and confirm that the issue remains the same. And if this is the case, either post step-by-step instructions how to reproduce the error or your model/geometry file.