DS Lite turns on for a second then shuts off after I replaced the case

Today i tried to fix my old DS-Lite (The case was broken) so i ordered a new one and swapped all the components over. Since i had a bit of trouble with the cable for the upper screen i think it may have got beaten a bit. When i turn the DS on the first right light flashes green for a second and the lower screen turns on for just a second then the DS shuts off. Could that issue come from the cable for the upper screen being broken or is there anything else that iam missing? (Sadly nintendo doesnt offer any repair service for the DS-Lite anymore cause i would have sent it in to get it repaired…)

I hope that somebody can help ^^

Thanks in advance