Hello there from California! You can try a fertilizer with a bit of nitrogen to give it a boost. My 20th century Asian pear was a very slow grower also and didn't come out of winter dormancy till very late, 2-3 months after the stone fruit were budding out. Now in its fourth year, it is catching up and growing like crazy. I would wait for the nitrogen fertilizer till next Spring, unless you are in early to mid Summer right now. You don't want to give it fertilizer and start it growing right before dormancy is supposed to set in.

Thank you for your reply!

So it is 20th century/shinseiki that is a slow grower?

I gave a bucket of water with 30-10-10 fertilizer last week and sprayed a bit on the leaves.

We had 104°F today, very hot, but everything is growing crazy, except it!

I can only say that mine seems to be very slow, compared to the rest of my 26 fruit trees. That fertilizer should be what you need but don't expect it to suddenly grow like a monster. I would expect some shoots to pop up. You might also try tipping the branches. That is, pruning the last several inches of a branch off to encourage branching. Fingers crossed you see some improvement! As an aside, we are taught to build up a layer of mulch at the base of the tree, covering the dirt up to the drip edge of the leaves. This keeps down weeds, cools the dirt where fine feeder roots are, keeps the soil moist longer, and as it breaks down, will feed the tree. It's not a must but for us in the hot inland deserts (It was 108 and stormy yesterday), anything helps.