I've had this issue from time to time.
Sometimes when I can't pass stuff, my anal anastomoses needs dilated. I self dilate now, so far so good. Are you feeling like you have stuff in there, but miserably are struggling to go? Have you ever had that issue?
Sometimes I feel like my bowels just get sluggish, too. I like a looser stool. MoM, about 15mls (I take at night; I'm continent, and usually it'll wake me up in 4 hours to go) works when things go this route. However to stay "loose," I take a 1/2-1 mag sulfate tab daily. Magnesium (like MoM) is an osmotic, so pulls fluid into the bowel. It's not a stimulant laxative, which is why I prefer it. Other meds have cramped me badly (even colace, oddly). I don't get much bump from grape juice, but some do.
Is your pouch older and more "efficient?" Mine can be, like I just absorb more water than you'd think a pouch would. My GI said this isn't super unusual, though here, on this site, especially with new pouches, people seem to have the opposite issue, mostly. Are you on Metamucil, Immodium, etc.? If so, stop that stuff. Drink plenty of water.
Another go-to in the past was a draught beer. Not bottled or canned, true draught. Think there's something in a keg that gets me going. Doesn't help as much these days. Wine used to, too, but i think my body's too used to it anymore!!