Green stuff poured on pcb withing plastic box .I dont know that green stuff and which cover all electronic component. Only connector cables and power supply cable is available.
The green stuff like a gel or jelly.
I guess he is not talking about solder mask but i think as you said a gel like substance sounds more of a glue to provide extra holding and firmness to components.
still do attach Pics they are obviously more helpful in understanding the query.