Trip Meter resets, remote not working....

I have an 06 Rio5 I just bought used. The speedometer wasn't working, they replaced the speed sensor. Picked it up tonight, when they went to inspect it they said they weren't getting a reading from the computer, I know it was sending out a reading when first purchased a month ago. The car has been at the shop a few weeks now. He told me something must have happened to the battery and I need to drive the car a few weeks and then it will show a reading. I had unhooked the battery before dropping it off to install a radio, I'm assuming that's why the computer needs to reset. When driving home from the shop tonight I stopped at the store. My remote wouldn't work, this one had been working second one doesn't even with new battery, when I came out and drove home I noticed the trip meter had reset itself. When I got home I turned it off again, restarted, it reset again. Also put new battery in remote that had previously worked, still didn't. Is this computer related? Alternator? Loose cable?? HELP!!!

Well I've fixed the trip meter resetting and remote not working. I didn't notice when I drove it home but dome lamp also wasn't working. Found the cluster, lamp and remotes all ran off one 10 amp fuse which was blown. Replaced and now those three issues are resolved. I'm still going to assume the computer not giving a reading was from me disconnecting the battery for the radio install and I haven't driven it enough to allow it to gather more info.