Developer unlock Windows Phone 8 : Error Code 0x64 -

we need unlock windows phone 8 device in order deploy our app still supports specific platform.
process working months ago without problem now, windows phone developer registration tool, available sdk 8.0, returns following error:

we have tried different devices (with date set correctly: utc +1 rome)

• htc 8s
• lumia 720
• nokia 625

all same result. have tried unlock our devices entire week, not seem temporary problem.

the devices , pc have both working internet connection , aren't running behind firewall/proxy @ all.

we have no problem @ all, unlocking wp 8.1 devices proper windows phone developer registration tool wp 8.1

do know if there's technical problem on microsoft side?
windows phone wp 8.0 unlocking process still supported microsoft?

as of may 13, 2015, can no longer developer unlock windows phone 8.0 devices. have upgrade them windows phone 8.1. don't have article point to, email received ms email address associated developer account:

if have windows phone 8.0 device use test apps, please read mail.

the windows phone 8.0 certificate validates developer unlocks expire today may 13, 7pm, pacific daylight time.

we recommend re-unlock windows phone 8.0 test devices prior today 7pm, continue testing 24 months.

after today, no windows phone 8.0 device able developer unlocked, , have 3 options continue testing windows phone 8.0 packages: – update phone windows phone 8.1 , unlock developer testing – submit apps beta through windows dev center , test windows phone 8.0 devices – test windows phone 8.0 apps via windows phone emulator

any windows phone 8.0 device unlocked continue unlocked , work test device until certificate expires. maximize time available test device, please lock unlock device before may 13, 2015 7pm pdt.

note change has no impact on apps available in windows phone store, has no impact on windows phone 8.1 devices, nor impact customers windows phone 8.x devices.

the windows store team