Why isn't Stairlift working after replacing batteries?

I recently replaced the two batteries in a Stannah 420 stairlift. The batteries were bad with corroded terminals. Stair lift would only move a few inches and then stop. Replaced the batteries noting the way terminals were connected but stairlift would not move. I did note some lights flashing on the control board but not sure of their meaning. Do batteries need to be charged for a while or what's the problem. Any help would be appreciated.