I've tried using /back in a few different scenarios, both as an operator and a normal player. Each time no matter if it's after /home, /spawn, or after death, it always returns as "Teleportation history is empty". I have the ftbessentials.snbt configured as follows:

teleportation: {
    back: {
	cooldown: 10
	enabled: true
	max: 0
	only_on_death: false
	warmup: 0
    }
}

I'm currently running version 0.1.0 in case this was addressed in a later version.

i found the probleme

you need too found the max size history, it's 0 by default, just change it too the value you want ( 10 is you have doubt )
in you're case the ( max: 0 ---> max: 10 )

Can't believe I missed that entirely, many thanks!