I don't know if it is my fault :( Can I enable a debug mode or something to see if there is an error?
BufferTag relies entirely on ctags for the results and hasn't been changed in a while. So check if ctags is installed and working properly on your system.
JSCtags doesn't properly with node v10. Sorry for the noise :(
The supported kinds are:
v global variables
By the way, I think kinds is more consistent terminology than types regarding the ctags documentation.