Error: Could not connect to the GlobalProtect gateway. Please contact your IT administrator.

• GlobalProtect Agent Error:  Could not connect to the GlobalProtect gateway. Please contact your IT administrator.
• PANGPA.log shows the following:

(T13736)Debug( 101): 10/26/20 09:20:06:110 connect failed with 5 seconds timeout.
(T13736)Debug( 599): 10/26/20 09:20:06:110 Failed to connect to <Portal/Gateway IP address/FQDN> on 443 with return value -1 and socket error 0(0)
(T13736)Debug( 784): 10/26/20 09:20:06:110 do_tcp_connect() failed
(T13736)Error(10527): 10/26/20 09:20:06:110 ConnectSSL: Failed to connect to '<Portal/Gateway IP address/FQDN>'. Disconnect ssl.
(T13736)Debug(10540): 10/26/20 09:20:06:110 Cannot get server cert of <Portal/Gateway IP address/FQDN>
(T13736)Debug(6060): 10/26/20 09:20:06:110 Already tried both ipv4 and ipv6 for gateway <Gateway IP address/FQDN>
(T13736)Debug(6070): 10/26/20 09:20:06:110 pretunnel latency (manual gateway) is 1
(T13736)Error(3473): 10/26/20 09:20:06:110 Failed to connect to gateway <Gateway IP address/FQDN>.
(T13736)Debug(5447): 10/26/20 09:20:06:110 Show Gateway GW01: Could not connect to the GlobalProtect gateway. Please contact your IT administrator.
(T13736)Info (2619): 10/26/20 09:20:06:110 Failed to retrieve info for gateway <Gateway IP address/FQDN>

• PA-3020
• PANOS 8.1.16
• Global Protect version: 5.1.5

• Certificate status shows: Expired 

•  Renew Certificate(s)
  1. If certificate has the following path:

==>> Root certificate 
=====>>Intermediate certificate
=====================>>GlobalProtect

• Renew Root certificate first.
• Renew Intermediate certificate second.
• Renew GlobalProtect certificate last.

2. Export certificate(s) under Device > Certificate Management > Certificate > select certificate > export certificate
3. Import certificate into client certificate storage  or push certificate to clients using  Group Policy Object (GPO )

• Generate a CSR (Certificate Signing Request)