I tried a different account this time and got the same error.
B4i Version: 5.51
Parsing code. (0.00s)
Building folders structure. (0.03s)
Compiling code. (0.01s)
Compiling layouts code. (0.00s)
Compiling debugger engine code. (0.64s)
Building Xcode project (0.18s)
Sending data to remote compiler. Error
Out: Build settings from command line:
ARCHS = arm64
CODE_SIGN_IDENTITY = iPhone Distribution: PPIC, Inc. (938DQ9AGXU)
CONFIGURATION_BUILD_DIR = /Users/administrator/Documents/UploadedProjects/<user id>/Payload
OTHER_CODE_SIGN_FLAGS = --keychain <user id>
PRODUCT_NAME = FirstApp
PROVISIONING_PROFILE = ee39768f-1817-4e6d-8b89-4801551dc228
note: Using new build system
note: Planning build
note: Constructing build description
Build system information
error: Missing private key for signing certificate. Failed to locate the private key matching certificate "iPhone Distribution: PPIC, Inc. (938DQ9AGXU)" in the keychain. To sign with this signing certificate, install its private key in your keychain. If you don't have the private key, select a different signing certificate for CODE_SIGN_IDENTITY in the build settings editor. (in target 'B4iProject')
Error: ** BUILD FAILED **