There's a well known diode issue that I referenced already. Did you watch the video?
Buy a multi-tester if you don't have one already, follow the steps in the video, and confirm whether or not the root cause is a failed diode.
If it is the diode issue, and it has failed open, then take the LEAF to an independent EV specialist shop (not Nissan!) and show them the video too. Details on how to install an inline diode, near the charge port, are provided here:
https://www.mynissanleaf.com/viewtopic.php?t=24696
I also created a PDF document on my OneDrive, which includes photos and detailed instructions, as I figured it's a common enough problem and photos on this site tend to end up with broken links:
https://1drv.ms/b/s!AjONM_UrXWS8-xr1VIZHnSyd4mqe?e=afmyti
Note: the cost of the diode is less than $5 and it might take a competent mechanic 30 minutes to do the work. Alternatively, if you have a friend that's an electrician then that person could do this job too. It's a pretty simple fix, if in fact the diode has failed and that's the only issue with the OBC.