Large Transport
Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 190
Human-Machine Interface; Communication Breakdown; Troubleshooting
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification
Procedure; Aircraft
While operating on NAT X; CPDLC and passing ZZZZZ to BIRD Flight Information Region (FIR) boundary; we received two ATC alerts - (white ATC EICAS message and audible ding). First ATC alert at XA:41; selecting ATC button on FMC; CPDC message was: This is an automated message to confirm CPDLC with Reykjavik Centre. We sent our response: 'Roger.' Less than a minute later; received a second alert at XA:42: 'Confirm assigned route.' We responded by selecting the prompts to confirm Route 1; and sent the response.Just to verify that all was well; I selected the ATC log page; which details all received and sent ATC messages. This is when we found an unanswered ATC message - also sent at XA:42- directing us to 'Squawk ZZZZ.' We answered the message with 'roger' and changed our squawk; so no real failure to follow ATC instructions occurred. What I wanted to point out with this report is that there were three messages sent from ATC within one minute - only two messages displayed when the ATC prompt was selected on the FMC; and if we had not investigated the LOG page further; we would not have known that ATC had sent a third message directing the new squawk. This is a potential safety point of failure; since it is not in our normal process to constantly check the LOG page to make sure that we are getting all our messages.
Captain of a Part 121 turbojet reported difficulties interfacing via CPDLC with ATC.