OpenLDAP Software does not support LDAPv2 (now historic).
OpenLDAP 2.x's slapd(8) can be configured to accept a version 2 LDAP Bind request, but expects requesting version 2 to speak a restricted, non-standard variant for LDAPv3 (basically LDAPv3 syntaxes and semantics in LDAPv2 PDUs).
To enable this, place the following in your slapd.conf(5) file.
This feature is only provided in order to support broken applications which request version 2 and then use LDAPv3 syntax and semantics in LDAPv2 PDUs.
This feature may be used to provided limited support for legacy clients using
the U-Mich LDAP variant of LDAPv2, sometimes referred to LDAPv2+, and possibly other variants of LDAPv2.
Use LDAPv3 instead!