Can't go back to lolipop from Marshmallow

[Ahmad Pajouhesh]

I already have PK1 MM ROM on my sprint s5, but I can't flash lollipop ROMs and Odin keeps failing.
How should I do that? Thanks.

 

[ironass]

I already have PK1 MM ROM on my sprint s5, but I can't flash lollipop ROMs and Odin keeps failing.
How should I do that? Thanks.

Have you disabled the Reactivation Lock?

 

[Ahmad Pajouhesh]

Have you disabled the Reactivation Lock?

Yes it is disabled

 

[ironass]

What exactly does it say in Odin when you get a FAIL?

Which stock Samsung firmware are you attempting to flash, exactly?

Is your device rooted and on a custom ROM?

 

[Ahmad Pajouhesh]

I tried to flash OG1 and OD3, but none of them were successful.
actually, I've tested on both rooted and nonrooted, custom and official Roms but they all fail. I have no problem with flashing MM ROMs.

 

[ironass]

Have you ensured that, "Repartition", is left unchecked in Odin?

Also, you appear to be flashing an old version of the Sprint firmware, OD3, that is for Android 5.0, Lollipop. If your bootloader is already on Android 6.0, Marshmallow, you may not be able to downgrade. To check which version your bootloader is, install Phone INFO ★Samsung★, free from the Play Store.

 

[Ahmad Pajouhesh]

yes, you're right.
it seems that my bootloader is on MM.
is there any way to downgrade it?