If no left Joy-Con controllers will charge, then it seems likely that your issue is with the connector of the left rail on the Switch tablet itself. Disassembly and cleaning of the contacts with high-concentration isopropyl alcohol or electrical contact cleaner may restore function if there's no damage. Alternatively, a replacement of the associated ribbon cable or the entire rail are options you may consider. I've attached an iFixit guide here that goes over replacing the entire assembly for reference.
I hope you manage to diagnose and resolve the issue without difficulty.
EDIT: Here's a link to another answer I've given that's relevant to my advice in the comment section. For cleaning (as well as investigation of damage for one end of the cable) this should be helpful, as it includes visual reference. The solution presented there was for intermittent function in handheld mode, but that's a symptom of the same problem area. In your case, function without charging implies the charging line/trace in particular has some issue going on somewhere. I hope you can isolate the problem easily with some good troubleshooting.
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
1