feedback from MPA40BT with acoustic guitar

Contributor - Level 1
Sorry for the dumb question, but I figure this is the place to get a good answer.
I have Behringer MPA40BT PA and a Taylor MIni-GSe bass guitar (acoustic) that i keep getting feedback from. I have added a sound hole cover and it helps, but I am still getting it?

I would try an FBQ100 but i need something battery operated as we are often playing outside at like a farmers market with no power.