From App Launcher, Search and Select NPSP Settings and work through the settings.
The NPSP Settings includes many areas of configuration for your NPSP org. The following are critical places for setup important for Donor 360.
Open People, Select Addresses
Verify Organizational Account Addresses Enabled box is checked
If unchecked, Click Edit, Tick Checkbox, Save
Open Relationships, Select Affiliations
Verify Automatic Affiliation Management box is checked
If unchecked, Click Edit, Tick Checkbox, Save