The Mathematica 12 in my computer cannot launch Chrome or Firefox session correctly. The first error message is
Import::jsonhintposandchar: An error occurred near character 'h', at line 1:3
I guess that the Mathematica cannot find my Firefox and geckodriver so I tried to add the install directory to the $Path of Mathematica but found it useless. The StartWebSession[] shows no option for me to assign particular external executable program for web-driver.\
I have tried to remove the paclet however it also seems have no effect.
OS: Windows10 Version 1909
MMA: version 12.0