I had one that had sucked up and disappeared a while back, I was moving things around in the tank and found it in the back under some rocks with no light and little flow. I thought is was a lost cause, but when I pulled it out, it showed signs of life as it kept trying to attach to the rock i set it on. I moved it back to the front of my tank with good lighting and moderate flow. It opened to no more than 1.5" across. I have been feeding it very small meaty foods like mysis and finely chopped krill and silversides. Now it is about 7 months later and it is about 8" across.
You said it has been like this for a month and a half? that is not normal. Mine with do this for a day or 2 when it splits. You might try gently moving to a spot with better light and different flow.