jitsi-meet: PKIX path building failed when I run jicofo.sh

When I follow this step from the Server Installation for Jitsi Meet:

Run jicofo:

=======
unzip target/jicofo-{os-name}-1.0-SNAPSHOT.zip
cd jicofo-{os-name}-1.0-SNAPSHOT'
./jicofo.sh --host=localhost --domain=jitsi.example.com --secret=YOURSECRET2 --user_domain=auth.jitsi.example.com --user_name=focus --user_password=YOURSECRET3

Then I get this error:

Jicofo 2017-10-28 22:42:06.108 INFO: [1] org.jitsi.xmpp.component.ComponentBase.loadConfig().202 Component org.jitsi.jicofo. config: 
Jicofo 2017-10-28 22:42:06.109 INFO: [1] org.jitsi.xmpp.component.ComponentBase.loadConfig().203   ping interval: 10000 ms
Jicofo 2017-10-28 22:42:06.109 INFO: [1] org.jitsi.xmpp.component.ComponentBase.loadConfig().204   ping timeout: 5000 ms
Jicofo 2017-10-28 22:42:06.109 INFO: [1] org.jitsi.xmpp.component.ComponentBase.loadConfig().205   ping threshold: 3
Jicofo 2017-10-28 22:42:06.640 SEVERE: [26] org.jitsi.impl.protocol.xmpp.XmppProtocolProvider.log() Failed to connect/login: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
org.jivesoftware.smack.SmackException: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader.parsePackets(XMPPTCPConnection.java:1060)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader.access$300(XMPPTCPConnection.java:982)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader$1.run(XMPPTCPConnection.java:998)
        at java.lang.Thread.run(Thread.java:748)
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
        at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
        at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1949)
        at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:302)
        at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:296)
        at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1514)
        at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:216)
        at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1026)
        at sun.security.ssl.Handshaker.process_record(Handshaker.java:961)
        at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1062)
        at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
        at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1403)
        at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1387)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection.proceedTLSReceived(XMPPTCPConnection.java:798)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection.access$1200(XMPPTCPConnection.java:150)
        at org.jivesoftware.smack.tcp.XMPPTCPConnection$PacketReader.parsePackets(XMPPTCPConnection.java:1055)
        ... 3 more

Please help me to fix it.