FR/GR drum not compatible with my GR 3750

[Flan]

Hello!
I just bought a red FR/GR drum for my recently acquired old GR3750 riso, but when I load into the machine, it says (translated from french) "wrong format installed drum".
How can a FR/GR drum not be compatible with a GR ? Is my GR too old for this FR/GR drum ? It does look newer than my GR black drum which works perfectly, for example.
Is there a way to make it accept by my machine?
Is there further specification that I have to look at before buying a drum ? I don't see any relevant information except for the "FR/GR" written on the top of the drum, the number (62913030) written on the handle, and some serial numbers written on the right of the "Caution" sticker on the front of the drum.


Thanks

[20gaugeO/U]

Which drums are compatible?

Are the drums physically the same length? GR 3750's took the longer drum, maybe you have a short FR drum? If they are the same length then remove the cover under the drum handle (4 screws) and check the dip switches on the board. May have color ink when it is set up for black, compare 2 drums