Looks to me like there is some guessing at the end. I know what should be there, but I'm not sure exactly how to get it in.

There are too many combinations for the center part... I give up.

..x..
.x.x.
x...x
.x...
..x..
.x...
x...x
.x.x.
..x..

Hmm i guess that didn't work.

Thank you, Michaenic.

Thanks for the help!

Thanks michaenic
in the middle it's an Epsilon sign.

Thanks for the hint.

As per the others, Thanks Michaenic. ? is the answer.

Sorry, that was meant to be an epsilon symbol but obviously this comment section won't recognize it so show a question mark.