If you open PDFs from Google Drive in the Team Drive folder you may notice that the Texthelp PDF Reader isn’t available from the Open with option
This is because permissions are different with the Team Drive folder than they are with your Google Drive folder.
To use the Texthelp PDF Reader with PDFs from the Team Drive folder PDFs must be saved to your Google Drive.
You can make a copy of the PDF if you don’t want to move the file from the Team Drive folder and save it to your Google Drive. Then the PDF can be opened with the Texthelp PDF Reader.