Execute the following command over your database (it's for nopCommerce 1.80):
INSERT [dbo].[Nop_Customer] ([CustomerGUID], [Email], [Username], [PasswordHash], [SaltKey], [AffiliateID], [BillingAddressID], [ShippingAddressID], [LastPaymentMethodID], [LastAppliedCouponCode], [GiftCardCouponCodes], [CheckoutAttributes], [LanguageID], [CurrencyID], [TaxDisplayTypeID], [IsTaxExempt], [IsAdmin], [IsGuest], [IsForumModerator], [TotalForumPosts], [Signature], [AdminComment], [Active], [Deleted], [RegistrationDate], [TimeZoneID], [AvatarID], [DateOfBirth]) VALUES (N'18c4f7dc-2964-41db-9611-8a313bf672d3', N'[email protected]', N'[email protected]', N'14F009DDBEF203EDC2124D54FA6D325E16E36D77', N'vw7zHZI=', 0, 78, 77, 0, N'', N'', N'', 7, 1, 1, 0, 1, 0, 1, 0, N'', N'', 1, 0, CAST(0x00009B3600C2192F AS DateTime), N'', 0, CAST(0x0000769B00000000 AS DateTime))