Nintendo switch help !

[Joetabs]

I’ve got an old Nintendo switch that was thrown up on by my son, after taking it apart and cleaning it, it now charges and comes on perfectly. I am having issues though with one of the joy cons, ( left ) where the joy con will connect wirelessly and charge when connected to the switch it self but the switch will not recognise it being connected to it physically. The right had joy con ( the working on) when you slide it to connect it it shows up a coloured line down the side of the screen, where as the left will not;

I have since tried different joy cons and again the same issue, I have also changed the rail in the switch body itself as previously it would not charge but since changing the rail the joy con does charge.

Any help would be appreciated.

Thanks