My phone finally showed an update as being available when I checked it today. It turned out to be MMB29M.----VVRU2CQI3, rather than the MMB29M.----VVRU2DQH2 that others had reported (upgrading, on my phone, from MMB29M.----VVRU2CQF2). It's only the last 3 characters that seem significant: from QF2 to QI3, rather than QH2.
At any rate, after I restarted the tracker (and did a couple of other things, but the restart seemed to do the trick), it synced, and has continued to sync. (It's adding bogus steps from my wrist's movements as I sit here and type! Yay!).
I'm going in to Verizon soon to upgrade my phone. Not to a Samsung, I can tell you that.