If you don't have the Global permission to create Next-gen projects, a "Connection lost" generic error is displayed when trying to create a Next-gen project in Jira Service desk.
- Navigate to Jira Settings > System > Global permission
- Delete public group in the Create Next-gen Projects permission
- Try to create a Service desk next-gen project
The project is not created, informing you don't have the permission to do it.
Add yourself to the global permission to be able to create the project and avoid the error.