As the title states, a customer's inverter is stuck in a Bootloop. Only batteries are connected and it's powered off. It keeps on booting up and down. 

What could be the problem?

Try to disconnect the batteries for a few minutes and then reconnect.

Does it indicate a charging source (AC-in or solar) on the display? I know you said neither are connected, but does it think one is? 

A charging source will keep the inverter from turning off, even if the switch (which is more a load switch than an on/off switch) is off. 

Also: VM II suggests it's a clone. It may be a poor quality one. 

Edited August 31, 20223 yr by Coulomb

Meccer with similar problem. After 2 attempts by agents to repair gave up and running for 2 years now offgrid.