This error indicate that you have trouble with license.
Try to stop all Ansys license from FlexLm and start him again.
In left corner from bottom of FlexLm you can see 3 field which offer information about running of Ansys. When you will stop running, than all those 3 fields must appear as stopped, but you when start it again then must be changed to running.
I hope it help you.
Only license and FlexLm is responsible by these type of errors.
Keep in touch.