I am trying to install Digital Sales Aid in the Sandbox but it keeps erroring out. I got the following errors. Has anyone faced this issue before?

Errors:
Entity is not accessible 
(DSA_Administrator) In Field: apexclass - no apexclass named DSAPostinstallscripttest found
(DSA_User) In field: apexclass - no Apexclass named DSAPostinstallscripttest found

Has anyone integrated Salesforce with O365 (SharePoint or OneDrive) for managing attachments? Also which is best solution for managing the files: SharePoint or OneDrive through this integration? I am basically trying to understand the pros and cons of integrating with O365 Sharepoint/onedrive.

I am trying to access one of my Customer Community pages and I can not access it from the Header bar. I can access it from SF "Communitites" "All Communitites" I can access "Mannage" and Builder from there. 
Why do I get the above error when trying to access it from the Global header area?

Any help greatly appreciated.
Adeline Moore