Invalid License ... 1 site, 2 x windows server, 2 x sambapos instances

This is the very first time I had this issue, usually it works on the following setup

1 site, 2 x windows server, 2 x sambapos instances (one on each windows server)

Installed license on server01 successfully, then The license on server02 will be kicked-off after reboot…

any clues ?

You cant install a license in 2 databases you must purchase an additional license. You can buy a 2nd license and license the 2nd database if you wish.