When you have a password exit implemented and make a REST call to the Automation Engine, no Host/computer Name information is returned.
Since the client is evaluating the Host information for security reasons this leads to failed logins.
20240118/091927.214 - XUC4PASS_Execute called with 1, "RESTAPI", "<user>", "<password>", 'E', "", 'A', 256, 0x0x7ffd47ad2a20
20240118/091927.214 - XUC4PASS_Execute exit with 1.
20240118/091927.221 - U00003234 Logon error: Access denied. (Connection='*CP005#00000013', host = '')
Solution:
Update to a fix version listed below or a newer version if available.
Fix version:
Component(s): Automation Engine
Automation.Engine 24.4.1 - Available
The reference for this fix is DE128232