Can't login to usermin suddenly

Hello, I have this problem. I am logged in Virtualmin port 10000 but when I am trying to login to a certain user pressing login to usermin button I get error server is not responding in port 20000. I checked the logs and I see only this: [18/Apr/2016:22:38:23 +0300] miniserv.pl started [18/Apr/2016:22:38:23 +0300] Using MD5 module Digest::MD5 [18/Apr/2016:22:38:23 +0300] Perl module Authen::PAM needed for PAM is not installed : Can't locate Authen/PAM.pm in @INC (@INC contains: /usr/libexec/webmin /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendo$ BEGIN failed--compilation aborted at (eval 15) line 1. Can anyone help me please? Thanks