Session stability feature does not work for VMs connected via Citrix Gateway when network is broken for more than 10 minutes.
However, if the connection is restored quickly after disruption, session reliability can work without issue.

Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

An STA ticket is created when launching a resource via the NetScaler gateway, and it remains valid only for a limited time by default.

If session reliability is triggered after the ticket has expired, the Delivery Controller's attempt to refresh or validate the STA ticket may fail, resulting in session launch issues.

Create below registry on DDC and restart Broker Service

1. Take a backup of HKLM\Software\Citrix\DesktopServer.
2. Create the below key:
Name: XmlStaRefreshableTicketLifetimeInSeconds
Type: REG_DWORD
Value: 500 (default) (The time in seconds for which a non-refreshable ticket remains valid)

Session reliability does not work for more than 10 minutes when passing through Citrix gateway