post man gives 500- severer error for authenticating purpose when i changed Secret in AppSettings  of appSetting.json file

Hi, 

I changed Secret as below in AppSettings  of appSetting.json file
```
"AppSettings": {
    "Secret": "5BFr#$14"
  },
```
then i  was getting 500- internal severer error for authenticating purpose by using postman.
Any one faceed this same issue and any solutions for above?

Many Thanks,