Huawei E5770

I got a E5770 locked to O2 that is on Firmware : 21.200.19.01.405.
It doesn´t allow me to downgrade to 21.180.99.11.00 and the unlock code I got doesn´t work on 21.200.19.01.405….
Is the unlock code linked to the Firmware or do I have a wrong code?
IMEI 867472020349240
Would love to have it unlock and get rid of the O2 surface.
Thanks!

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