Can I trust my RV LiFePO4 battery?

Four years ago, I bought a StarkPower LiFePO4 battery for my truck camper. During that summer, the battery performed wonderfully. It was far more satisfying than the heavy lead acid batteries.

However, three years ago I injured my shoulder and my camper sat idle for two years. When I finally felt able to use the camper again, I found the battery showed zero volts. I put it on the charger anyway, but the charger gave no indication that it even recognized that it had something connected to it. A friend advised to just leave the special lithium ion charger on the battery for a day and it could revive the battery. 

I was surprised when that proved to be true. A day later, the charger showed the battery fully charged and ready to go.  It kept working through the four day camping trip without trouble.

Unfortunately, circumstances left the camper idle for another year.  

Now I have use for the camper again, the battery is showing zero volts again and I'm not sure of I should try to revive it again.  It's not a convenient time to have a lithium battery fire.

The manufacturer of this battery is no longer in business. I cannot call them for technical assistance.  Does the abuse of idleness render this battery unsafe?  My research is inconclusive.