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Check the battery - take it out and put it back in after wiping the terminals. Or, replace the battery.
How old is your Mini8, and how often have you used it before with exactly this type of film, please?
If you have followed all the instructions that came with it, we may presume that it is defective, and needs to be returned, as a defective product, to the store or vendor that sold it, for an exchange for another or equivalent camera.
But if you had no instructions to follow, that's a different case.
Let me know which case it is, and - as needed - I will advise you further. Thanks.