trunk lock won't turn w/ key - 2010 Yaris Sedan

[TYaris2010]

used 2010 Yaris, 50k miles, car is relatively new to me.

Putting key into trunk lock, it will not turn (OEM key). As I haven't used the trunk, it must've been this way when I bought it but I didn't check when buying.

Sprayed Some PB Penetrant (similar to WD 40) to clean out gunk or whatnot, still no luck. Did this a few times.

Anyone else have this issue? how did you solve it?

Car is not old so I cannot believe that the cylinder is worn out. I am guessing the prior owner used the trunk release in the car versus the key on the trunk? so it got dirty over time & seized? or?

Any tips appreciated. Do not want to pull and install a new cylinder unless I have to.

Door locks work fine.

Have considered trying graphite in the lock but as of yet have not.