Overview
When using Adyen payment terminals integrated with a POS system, you may occasionally encounter errors such as:
“Terminal not responding”
Dropped or incomplete transactions
POS freezing after EMV prompts
Terminal reconnecting only after restarting the POS
In many cases, these issues are caused by network connectivity interruptions between the POS system and the payment terminal, rather than a hardware or configuration issue with the terminal itself.
This guide outlines the most common cause and the recommended troubleshooting steps.
Common Cause: Network Session Timeout
Adyen POS integrations typically rely on a persistent network connection between the POS system and the terminal using the Terminal API.
The POS maintains an active session with the terminal in order to:
Send transaction requests
Perform status checks
Process cancellations
Receive transaction responses
If the network drops or interrupts this connection, the POS may lose communication with the terminal and display errors such as “terminal not responding.”
This may also result in:
Transactions that appear to stall after card interaction
POS requiring a restart before reconnecting to the terminal
Status checks failing intermittently
Common Network Causes
These issues are most commonly related to the merchant’s network infrastructure, including:
Firewall Session Timeouts
Some firewalls automatically close idle connections after a certain period of time (for example, 1–5 minutes). When this occurs, the POS system loses its session with the payment terminal.
Network Security Appliances
Security appliances such as:
SonicWall
Fortinet
Cisco Umbrella
Sophos
Meraki
may terminate persistent connections used by payment terminals.
Managed Network Switches
Managed switches may introduce traffic filtering, connection timeouts, or network inspection that can interrupt terminal communication.
Troubleshooting Steps
1. Verify Terminal Status in Adyen Customer Area
Confirm the terminal appears Online in the Adyen Customer Area.
Steps:
Log in to the Adyen Customer Area
Navigate to In-person payments
Select Payment devices
Locate the terminal by serial number
Review the following:
Device status
Last activity timestamp
Connection type (Ethernet, Wi-Fi, cellular)
Frequent changes in activity or connectivity may indicate network instability.
2. Review Terminal Activity or Event Logs
Check the terminal event logs for indicators such as:
Connection lost
Network reconnect events
Session interruptions
These events can help identify whether the terminal is losing connectivity with the POS or Adyen platform.
3. Confirm Terminal Software Version
Outdated terminal software can sometimes affect integrations or remote support functionality.
Check that the terminal is running a supported and up-to-date firmware version.
Recommended Network Test
A quick way to determine whether the merchant network is causing the issue is to perform a hotspot test.
Steps
Enable a mobile hotspot on a phone.
Connect one payment terminal to the hotspot.
Process several transactions.
Results
If the terminal works normally on the hotspot, the issue is likely related to the merchant’s network configuration.
If the problem persists, further troubleshooting may be required.
Network Configuration Considerations
If network restrictions are suspected, the merchant’s IT team may need to ensure the following outbound connections are allowed:
TCP Port 443
TCP Port 8443
Additionally, firewall or security appliances should allow persistent outbound connections to Adyen services.
Best Practices
To maintain stable terminal connectivity:
Avoid aggressive firewall session timeouts
Ensure network appliances allow persistent outbound connections
Keep terminal firmware up to date
Use stable wired connections where possible for fixed terminals
When to Contact Support
If issues continue after completing the troubleshooting steps above, gather the following information before contacting support:
Terminal model and serial number
Description of the error message
Time of the most recent occurrence
POS system being used
Network environment details
Providing this information will help expedite the troubleshooting process.