Andy Karl talked about this a few months ago on the “I Wanna Be Like You” podcast. In summary, they still want to put it out, but they didn’t get the reception they hoped/expected, and they were coming in at a time that other shows were being filmed/released (Hamilton, Come From Away, etc) that were more popular at the time, and deals fell through, etc.
Jersey Boys already had a less-than-stellar film adaptation, and was doing the cruise chip circuit for a bit. It’s going out on 20th anniversary US & UK tours (mostly two-night stints) this fall, maybe they’re hoping it will garner some more interest for a future release. A quick glance at the show’s active socials tells you there isn’t a whole lot of demand for the property at the moment.
Nick did perform some Frankie Valli a few nights ago, so it’s possible they’re just awaiting for the right time to try it again. Sadly the real Frankie Valli had to cancel the rest of his tour due to health concerns (which should have prevented them from touring again in the first place, IMO).
I am big. It’s the REVIVALS that got small.