Need to check if the issue is with only for Specific users or all the users who are using XfilesPro, Based on that follow the below steps.
If it is for all the Users then follow Scenario1 , Only for specific users then follow Scenario 2 , 3 and 4
Scenario 1: Check if connection is there are not(From storage setup)
Below is the step to check the above point:
Go to XfilesPro Application > Click on Storage setup > Manage/Info > Check if the root site name is there are not, if it is empty then the connection is broken!
To fix this, we need to reconfigure the connection and please follow this article to resolve the issue
Scenario 2: Check if User has a XfilesPro Custom Permission(Including the XFP_Folder_Structure__c filed)
From quick find > Search as Permission set > XfilesPro Custom permission > Check in which object the issue is occuring > Check the XFP_Folder_Structure__c field has read permission or not, it it is not enabled please enable!
Scenario 3: Check if user has a Xfiles custom objects field level permission(like External_Content_Details__c, Cloud_Storage_Provider etc)
From quick find > Search as Permission set > XfilesPro Custom permission > Check the objects of External_Content_Details__c, Cloud_Storage_Provider, XFP_Object_setup for these objects all the fields should have Read level access!
Scenario 4: Check the upload in external storage
Check the storage limit in the provider end, and In other scenario, check from the provider end if the user has a access to upload a file from the drive end, if not please provide the required access