The file size limit for connected spreadsheets is 5MB. If you're seeing the error message WARNING: This worksheet is too large to import, it's highly likely your file exceeds this limit.

Even if your file size is lower than the 5MB limit, .xlsx files use ZIP compression within them. This means a 2–3MB file could roughly be about 10 times the size reported on your device.

We recommend importing .xlsx file to Google Sheets. You can then use ImportRange to reference the data from the converted file.

An alternative option is to export the .xlsx spreadsheet to a .csv file and use ImportData to import that data into Google Sheets.

We recommend using ImportRange to feed the data you need from the original spreadsheet into a second spreadsheet, leaving the original untouched.