If more than one certificate is present in the Personal Certificates pool then you must specify the certificate used for authorization service in the ACCCMUCAProxyService.exe.config file of the UCA proxy service.
Procedure
Stop the UCA Proxy service.
Change to the directory to <install_path>\Services\ACCCM UCA Proxy Service
Open the ACCCMUCAProxyService.exe.config file.
Set the valid certificate thumbprint value for "BreezeAuthorizationCertificateThumbnail".