Login to CP fails with the following error:
"Error: Your session has expired due to inactivity".
The issue happens when a customer is logged in both to CP and the store. Two sessions with different lifetimes are created, and when CP session expires store session is still active. When a customer whose CP session is expired but the store session is active tries to enter the CP, he or she sees the message "Error: Your session has expired due to inactivity".
Such behavior was classified as the software issue PBAS-28540 and fixed in OBAS 4.5.6.
To resolve the issue, please upgrade to 4.5.6 as described in How to upgrade OBAS system to the latest available version.
The workaround is to close the browser so that the store session is over. After that a login screen is shown and log in is possible.