Hey Anvi, this error generally comes when you have provided machine key of different machine (other than your machine). So first cross check once, next check for Orchestrator URL. Since latest update of Community Orchestrator please be careful when connecting Robot to Orchestrator. Earlier you simply need to add this URL:
https://platform.uipath.com/
Now you need to provide full address like:
https://platform.uipath.com/[AccountName]/[ServiceName]
![image](https://aws1.discourse-cdn.com/uipath/original/3X/7/6/76fe73036c0533130cf9eca912436623cac2f12e.png)