"illegal_argument_exception: rollover target [.siem-signals-spacename] does not point to a write index",

We are getting error mentioned below under kibana -> Security -> Cases; can someone please assist me on how I can fix it and why I am getting this error?

what I understood from elastic document and also noticed in index alias that for 8.0.0 or later the alerts-security.alerts-spacename alias will be use not .siem-signals-spacename We recently migrated from 8.0 version to 8.3.3 version.

{
  "name": "Error",
  "body": {
    "message": "illegal_argument_exception: rollover target [.siem-signals-spacename ] does not point to a write index",
    "status_code": 400
  },
  "message": "Bad Request",
  "stack": "Error: Bad Request\n    at fetch_Fetch.fetchResponse (http://myserver/bundles/core/core.entry.js:1:123392)\n    at async http://myserver/bundles/core/core.entry.js:1:121448\n    at async http://myserver/bundles/core/core.entry.js:1:121405"
} 

Thanks in advance Nivedita