The Trump administration was not invited to the gathering in Santa Marta, Colombia. A White House spokeswoman called the green transition “destructive.”
Agreement to conduct the necessary phase out is probably not possible if a country run for the benefit of the oil industry is involved in any meaningful way
The fact that they invited only limited number of countries suggests they are done with unanimous consent and are looking for countries that actually want to do something instead. So if majority of countries want to do something and Canada will be trying to block it they can just ignore it and do it without Canada.