Robot vaccum not docking itself

From past month or so Robot vaccum is not docking back to the base station and had do it manually everytime.. base station is placed exactly the same place as before not changed at all, out of sudden this issue started happening.. robot keeps trying n trying to get to the station but at the end it stops infront of the base and had to manual place it back.. rest all functions are working flawlessly, please help me here

Hi,
Please check the charging contacts for black carbon mark/deposits. You may need to scratch it off from the contact points of robot/station. You can share pictures of that so that we can understand better. Thanks