Profile Question

How many profiles can Horizon mod on 1 usb? I have 3 profiles, 2 of which I can mod. Tried to mod my 3rd profile and I can’t do it. I have moved it from my HD to the USB but the profile comes up with no affinity for my account. I did have to reload this account as I wiped out all the progress when trying to mod it before. This is for Forza 4. :confused: