I suspect that most likely that they replaced Nokia IP Appliances, which ran VRRP which is usually where come across people using Gaia VRRP.
However I can answer this one for you.
VRRP works on a Priority and Priorty Delta.
The Priority is the BOX priority and the Priority Delta is the change made to that by each Interface.
If you look in the Gaia Portal then look at the Virtual Router.
TYPICALLY people set a Priority with a difference of 10 between the two boxes, ie 100 and 95 with a Priority Delta of 10.
IF one of the Interfaces fails then this will subtract 10 from the Priority, so would drop the 100 to 90 which being lower then the 95 on the Second Unit would cause the system to failover.
So if you want to force a failover then look at the two units to see what the Priority is set too and adjust one of the units Priority, ie if the 1st is 100 and the 2nd 95 then make the 2nd a Priority of 105 which will then give that the higher priority and then cause the failover.
Then if want to move back then change the Priority back to 95.
https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solut...
Gives details on how to configure VRRP and goes through how it works as a nice refresher.