"Error: Insufficient permissions" or "Error: You don't have the required permissions to perform this action." in Nonprofit Success Pack When Deleting Contact (NPSP)

To be to Manage, either Merge or Delete Contacts in a Household, a user/profile must have the following Object Permission and Field Level Security. To give this access:

1.) Go to Setup

-In Salesforce Salesforce Lightning click in the gear in the upper right, then on "Setup", on the next page on the left in the search box type in "Profile", click on "Profile", then on the Object Access you want to update

-In Salesforce Classic click on "Setup" in the upper right, on the next page on the left in the search box type in "Profile", click on "Profile", then on the Object Access you want to update

2.) Go to each Object below, and then for each Object give the "Read" Permission to the corresponding Field/s

Object ----------------Field/s

• Account----------------Name
• Case--------------------Account Name, Case Number, and Contact Name
• Opportunity------------Account Name, Opportunity Name, Primary Contact, and Stage
• Recurring Donation--- Recurring Donation Name and Contact

3.) Make sure that the User/Profile has Delete Access 

• Account (this applies for Merging Contacts)
• Contact
• Opportunity
• Recurring Donations