This post will help u in recovering the IMEI of your a63.
IMEI becomes invalid or null due to the corruption of nvram this can be corrupted in any way.
Note:-U should backup any important files present in phone memory(sdcard1)
Bcz this proceedure will format everything.
2.Sp flashtool v3
3.Micromax a110 drivers(dwnload frm micromax website)
1.remove battery,sim,sdcard etc
2.dont put battery
3.then connect ur phone to pc without battery(if not wrking Then put on battery)
4.in sptool click format option
5.select 2nd option i.e.dont frmat bootloader
6.after succesfl format
7.flash the stock firmware....
And Hooray u did it .....