Joining wifi pattern on status LED, but IMP doesn't connect in the end

My Imp doesn’t connect to wifi and blinks with following pattern
According to blinkup guide
its connecting to wifi network, but after 60 seconds device sleeps.
All my other devices are happily connecting to my router, so cannot blame network as an issue.
Moreover this issue started to appear only after firmware upgrade.

That flashing code is generally the sign of an incorrect password or mistyped SSID. Tried double-checking and blinking up again?

yup tried several times.
Tried to connect to two different networks as well. Dint work

Is the imp accepting your blinkup? (ie, is there a short green flash at the end of the blinkup process?). If there isn’t then it has not accepted/stored the new data and is just re-using the old config.