When I switch from on LVWeb site in one browser tab to another LVWeb site in another browser tab I occasionally get prompted to log in again, and no data flows in the cards until I refresh, maybe twice.

Known limitation

This is a known limitation when using TIBCO LiveView™ Web with current (as of early 2019) browser versions.

The behavior is that when using one browser with two or more LiveView Web sites pages open in two or more browser tabs, clicking away from one LVWeb site to another and back again results in no data flowing to the page. After a Reload (key F5) the browser prompts for login username and password again and data still does not flow. 

This error appears in most cards (id will be different):

An error occurred while fetching data: Invalid session '4068bed7-7921-4794-9dc1-3bb6d99fcc7f'

A second Refresh (key F5) is needed after logging in again to restart data flowing. This cycle will repeat switching between sites and LVWeb pages.

This was seen using:
TIBCO LiveView™ Web -- 1.4.1
Google Chrome -- 74.0.3729.131
Mozilla Firefox Quantum -- 66.0.5
Microsoft Internet Explorer® 11 -- 11.472.17134.0

This was not seen when opening only one LVWeb site in multiple browser tabs (in this scenario the login credentials are shared).

This appears to be due to how current browsers associate cached user credentials with multiple sites.