Reader for Mac keeps needing permission for Google Drive

[ロロ5FE8]

The reader DC on my MacbookPro does not keep connection to Google Drive. 

Even once it was granted for permission to my Google account for viewing and editing whatever, after around 1 hour, suddenly got logged out from the account and I have been kept enforcing to make a re-logging in procedure to grant the permission.

I think it looks not a proper movement. Does anybody have the same problem

OS: BigSur 11.01
Reader ver: 2021.001.20149

[ロロ5FE8]

lost some sentences while posting anyway, of course, solutions are welcome too if you know. 

[ロロ5FE8]

In addition, the checkbox on the authorization screen to Google drive , for keep signing on, has been already checked.