Not able to start/create process/project in UI path 2021.4.1 . getting error as Data at the root level is invalid. Line 1, position 1

Thank you. It is possible that the issue was caused by corrupted installation. For that you could try to reinstall by following this guide How to fix your Studio installation / Licensing issues

But before you do, could you maybe search your Windows Start menu for the Diagnostic tool from UiPath and send me over the output via a private message @loginerror? We would like to investigate it a bit more to make sure no sneaky bugs make it to future releases.