Why this error?

This error happens for two main reasons:

1. Google Sheets API is temporarily down

Google's services are having temporary issues. This usually resolves itself quickly.

2. Your spreadsheet is too complex

Google doesn't provide much detail, but they confirm that spreadsheets with high complexity can trigger this error. This includes:

• Very large spreadsheets (thousands of rows)
• Heavy formulas or complex formatting
• Multiple sheets with lots of data

The Sheets API returns a 503 error when the service is unavailable or when the complexity of the request or spreadsheet is high.

source: Troubleshoot Sheets API errors - google.com

How to fix it?

If it's a temporary Google issue

Simply wait a few hours and retry your bot. The service should be back up, usually shortly.

If the error persists (spreadsheet complexity)

If retrying doesn't work after several attempts, your spreadsheet might be too complex:

1. Create a new, simpler spreadsheet and update your bot to use it
2. Reduce the number of rows - archive old data to another spreadsheet
3. Simplify formulas and formatting if possible