Good to hear that you’re able to start narrowing down the root cause. As for the size limit, there’s no size limit on the Looker Studio (Pro) side per se, but the size restriction is instead on the Google Sheet/Google Drive side.
Spreadsheets
- Up to 10 million cells or 18,278 columns (column ZZZ) for spreadsheets that are created in or converted to Google Sheets.
- Up to 10 million cells or 18,278 columns for spreadsheets imported from Microsoft Excel. The limits are the same for Excel and CSV imports.
- When you convert a document from Excel to Google Sheets, any cell with more than 50,000 characters will be removed in Sheets.
- Up to 100k rows for pivot tables in Connected Sheets.
- Up to 500k rows or 5m cells for extracts in Connected Sheets.