I am getting an System Error message when I try to su to an user. I am using Ubuntu 18.04 and version 1.16.1-1ubuntu1.3

Jul 29 11:55:17 su[8658]: pam_sss(su:auth): authentication success; logname= uid=1000 euid=0 tty=/dev/pts/0 ruser=**** rhost= user=***** Jul 29 11:55:17 su[8658]: pam_sss(su:account): Access denied for user *****: 4 (System error) Jul 29 11:55:17 su[8658]: pam_acct_mgmt: System error Jul 29 11:55:17 su[8658]: FAILED su for ***** by *****