I self-installed a dishwasher which I am certain works correctly. I
hooked it all up and ran it. Water does not drain out of it. I took
out the dishwasher, unhooked the hose and inspected it for
obstructions; none were found. The remaining water in the dishwasher
drained out once disconnected, so there was no obstruction from the
interior of the dishwasher to the hose hookup.

Having established that there is no obstruction preventing water from
draining... what could it be? This is the 2nd dishwasher I have
attempted to install and the 1st one also had the same issue, so I
find it difficult to believe that replacing the dishwasher again would
solve the issue.

Thanks in advance for any helpful advice or suggestions you may have!