2010 Prius no Multifunction Display visible

Due to the trunk lid not being closed tight the regular battery wore down to a no start situation. Tried to jump from post in fuse box but battery cables did not seem to be getting a good grip. Changed to a battery charger that had a start function. Car started but the multifunction display In center did not come back up. Dealer wanted $140 to just look. No thanks. Brought car home and was going to hook up battery charger to do a rapid restore to battery. I found the negative battery cable loose. Tightened same and display is back up. Just thought others may want to check this if they have a similar problem.