Can't shift into 5th gear.
RIDE SPECS: 2006 Honda Civic SI (coupe) 150,000 miles
Today I decided to tackle some routine maintenance things I've been neglecting for some time. First thing I did was change the spark plugs out and replace with NGK Iridium plugs. Next I did a coolant flush and filled with Honda Type 2 coolant. Lastly I drained the tranny and put about 1.6 (ish) qt of Honda manual transmission fluid back in. After everything was buttoned back up I burped the cooling system for a while, cleaned up and had myself some dinner. Come back out to take the car around the neighborhood to make sure everything is copacetic and come to find that I am unable to shift into 5th gear. All other gears have no problem, just 5th. I have no idea what could be causing this issue, possibly too much air in the transmission? Any input would be really appreciated.