Lets fix this sound system.?

Hi. I have an Alpine MRP-M650 amp. It has 2 30 amp fuses. The manual tells me to add a 40 amp fuse next to the battery. I currently have a 70 amp fuse instead but the amp doesn't turn on. This is the first time I try installing this amplifier. What kind of fuse should I use? By the way, I am using 8 gauge wire and the amp is under the penger front seat. Any other reason why it doesn't turn on? Thanks friends.