Error -1003 means Parsec cannot write its authentication file to the default directory. This is almost always a permissions problem on that directory, but a full disk or a non standard file system layout can cause it too.

Where Parsec stores this file

• Windows: %appdata%\Parsec or %programdata%\Parsec
• macOS: /Users/Shared/.parsec/ or /Users/USERNAME/.parsec/
• Linux and Raspberry Pi: /home/USERNAME
• Android: the app's external data directory, which varies by device

On macOS, .parsec is a hidden folder. In Finder, press Command + Shift + Period to show hidden files, or use Go then Go to Folder and paste the path.

How to fix it

1. Open the directory for your platform and install type, listed in Where Parsec stores this file.
2. Create a new text file there and try to save it. If the save fails, your user account does not have write permission to that directory.
3. Grant your user account write permission to the directory, or ask whoever administers the machine to do so.
4. Check that the disk is not full.
5. Start Parsec again.