There error is generally occurs when the LDAP version requested by the client is not supported by the server.
The OpenLDAP Software 1.x server only accepts version 2 LDAP Bind requests. Note that 1.x server expects U-Mich LDAP, an LDAPv2 variant, to be used. This variant is sometimes referred to as LDAPv2+.
The OpenLDAP Software 2.x server, by default, only accepts version 3 LDAP Bind requests but can be configured to accept a version 2 LDAP Bind request. Note that the 2.x server expects LDAPv3 [RFC4510] to be used when the client requests version 3 and expects a limited LDAPv3 variant (basically, LDAPv3 syntax and semantics in an LDAPv2 PDUs) to be used when version 2 is expected. This variant is also sometimes referred to as LDAPv2+, but differs from the U-Mich LDAP variant in a number of ways.
Use of LDAPv3!