I’ve been having the same issue, but was able to get my two subscriptions that needed to be cancelled to go through finally. However, I’m not sure if it was pure luck, or if I caused some weird glitch in the system?!?
So I was in settings, and had the page pulled up showing all my active Apple app subscriptions in settings(on iPad, not my iPhone, although it could work on either who knows?). I had already tried selecting one of the apps I wanted to cancel my subscription with. It asked me to confirm, I clicked it, box vanished… “cancel subscription” letters in red turned to grey for maybe a second, then straight back to red(meaning it failed to cancel).
So out of pure frustration, I continued clicking back on that same app subscription, then clicking “confirm” on the pop up box as quickly as possible, over and over again(I believe it took 6 times). Eventually, it sort of acted like it was going to freeze(like as if the app was going to crash and force close) for maybe 2-3 seconds and then it cleared itself up. To my surprise I was back at the app subscription page of settings and the subscription I was attempting to cancel, had in fact cancelled!!
I was able to duplicate this outcome again on the second subscription I was wanting to cancel. So, still not sure if it was luck or some weird glitch. But maybe it will work for some of you, or help someone..
Sorry for my poor grammar, spelling, punctuation, and overall writing etiquette. Math was my subject in school, English/Lit however, was not! Best of luck!