Did you read this? Problem with July 30 2020 Version: nb184 no longer able to write and read files - #15 by Anke
... and please read the complete thread.
Do you have another test device with Android < 10?
Try this for your Android 10 device:
Copy / move the csv file to the ASD (app-specific directory):
/storage/emulated/0/Android/data/edu.mit.appinventor.aicompanion3/files/...csv
On your device: → Internal Storage → Android → data → edu.mit.appinventor.aicompanion3 → files
and put these blocks in your app:
