The actual reason why humans and chimps don't produce hybrids is probably not the chromosome 2 fusion.
Differences in chromosome counts often do cause sterility in offspring due to problems with meiosis (which is the reason why mules are almost always sterile). However, after a chromosome fusion there is a short window of evolutionary time where meiosis is able to work (otherwise the fused-chromosome mutation wouldn't be passed on and spread through the population). The real reason species that can't produce hybrids aren't able to is that the longer they have been diverging from each other, the more unique mutations they accumulate in their genomes. Each new unique mutation that becomes fixed in one species has never seen the unique mutations that became fixed in the other species, meaning there is a chance they are incompatible (these are called "Dobzhansky-Muller Incompatibilities"). The longer two species have been isolated, the more unique mutations they each have that have never seen the ones in the other species, so the chance that two mutations are incompatible grows exponentially over time. This is the real reason why species with different chromosome counts can have sterile offspring - eventually enough mutations build up between the fused chromosome and its unfused counterparts that meiosis can't pair them together