Our server is showing the error "LDAP initialization failed, Check LDAP and restart apache". The apache screen shows the following:

Configured LDAP was found ready to use.
NIF CertHandler: Root certificate file for master ldap not found, requesting a new one from server.
NIF CertHandler: # Root Certs=1
NIF CertHandler: Retrieved certificate of size=1330.
*MASTER[] [-1] ldap_simple-bind : Can't contact LDAP server (81)
ldap *MASTER[] down
LDAP initialization failed. Check LDAP and restart apache.

it then cycles the same message...any clues on where to start and what to check? Thanks in advance...