Files Connect: Quip is not a Selection When Creating an External Data Source in Salesforce

Possible causes for this would be either the user is not added to the Quip permission set that was created or the permission "Files connect cloud" is not enabled for the permission set. Please make sure that you are meeting the below criteria while creating a permission set for Quip:

1 - Create a permission set for Quip with "Files Connect Cloud" permission enabled under system permissions. 

2 - How to enable "Files connect cloud" permission in the permission set.

• Click the permission set you created earlier on the Permission Sets page.
• Click on "System Permissions" 
• Click on edit at the top of the page
• Search for "Files Connect Cloud" under permission name - check the box and save the changes.

3 - Make sure that you have added the users in the permission set that was created for Quip.

• Click the permission set you created earlier on the Permission Sets page.
• Click Manage Assignments.
• Click Add Assignments.
• Select the checkboxes next to the users you'd like to assign permissions to, and assign them.