Received the following error message with a Microsoft Dynamics Nav Client:

The client could not establish a connection to the Microsoft Dynamics NAV Server.
FaultCode = 'Invalid Security'
Reason = 'An error occurred when verifying the security for the message.'

The fix is a simple one. Make sure the date / time is correct both on the client, plus also the server.

Microsoft allow a time difference of up to 5 minutes between client/server. Over 5 minutes is typically not allowed as this can allow “replay attacks” (where credentials and authentication is replayed again at a later date).

A simple explanation of a “replay attack” is available here.

The setting can be changed in Group Policy, but I’d recommend keeping this to the 5 minutes by default.

https://docs.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/maximum-tolerance-for-computer-clock-synchronization