Like Nokia before it, Sony has always found it challenging to break into the US smartphone market. Things looked like they were turning around in late October of last year when T-Mobile started selling the much-improved Xperia Z3 and Verizon also got involved with a customized Z3v variant, but now they appear to be unravelling again. T-Mobile has quietly pulled the Z3 from its online store, directing customers to a pair of refurb handsets, the Xperia Z and Z1S, as the only options it offers under the Sony brand. Verizon's Xperia Z3v remains available to buy from the carrier, but this is still a significant (and so far unexplained) setback for the Japanese company.

@Serotheo The Z3 is no longer available. Here are our current Sony devices: http://t.co/ijK7q3PuYq *JB — T-Mobile (@TMobile) April 5, 2015

T-Mobile is likely responding to a lack of demand by yanking Sony's flagship phone, though Sony hasn't helped its cause with a particularly slow rollout of the latest Android update. Android Lollipop was announced at the same time as the Z3 went on sale, but Sony's upgrade to that software is only now starting to roll out. At a time when competitors' flagship phones are either already running Lollipop or being upgraded with even faster devices that have it preloaded, the Z3's luster is rapidly starting to fade.

Early leaks of the Z3's successor, the presumed Xperia Z4, point to an almost unchanged device. The look remains the same and the internals are predictably updated with the newer Snapdragon 810 processor from Qualcomm. Given the backlash that HTC elicited when it released the One M9 with just subtle design tweaks and the same processor upgrade, Sony is facing an uphill struggle in trying to catalyze excitement for its next big phone release — at a time when its incumbent flagship is losing its place on store shelves.