Error: Unity Cannot Build Player While

What's Causing This Error

The Unity error message 'cannot build player while' usually surfaces when there is an ongoing process in the Unity editor that hasn't been finished or terminated properly. These processes could range from scripts that are still running, asset import operations not yet completed, or perhaps scene loading that is currently underway.

Sometimes, this error can also be a result of inconsistent or corrupted project files. If the Unity editor isn't able to read or access necessary files due to corruption, it wouldn't be able to build the player effectively, leading to this error.

Solution - How To Resolve It

1. Stop Ongoing Processes: Close and reopen Unity to ensure all running scripts or operations are stopped. This is the simplest solution to try first.

2. Isolate Problematic Scripts: Disable scripts one at a time and try the build again until you find the one causing the issue. Look for scripts that may be stuck in infinite loops or long-running operations.

3. Complete Asset Imports: Check your 'Project' window to see if there are any assets currently being imported. Allow them to finish, or cancel and retry the import operation.

4. Regenerate Project Files: Use the 'Regenerate Project' option by right-clicking your project in the Project window and selecting 'Regenerate Project'. This can help resolve issues caused by corrupted project files.

5. Clean Build: Try performing a clean build by going to 'File' > 'Build Settings', selecting your desired platform, and clicking 'Build'. This will force Unity to rebuild all necessary files for the player build.

6. Revert to Backup: If you have a backup of your project, revert to a version of the project where the build was working correctly.

7. Create a Fresh Project: As a last resort, create a fresh project and slowly migrate your assets and scripts to the new project. Always make sure to back up your projects before doing so to avoid any data loss.

If none of the above solutions work, consider seeking assistance on the Unity forums or from the support team, providing details about what led to the issue.