Possibly there was a pathogen in the soil, or there is something else going on that is coincidental. Time will tell, if it never leafs out again you will then know there was a problem.

You said "I can't remember the ratio, but I did use a lot of the manure."

That could be a problem.

Even when one plants a woody in the ground, the suggested procedure is this:
No fert in the hole; if you absolutely must fertilize, add it to the soil surface & water in.

Effective fertilization is always based on individual circumstances and not blanket generalizations. Trees in deficient soils do very much need to be fertilized, same as any other plant. A tree is basically a sort of woody high rise with the new shoot and root growth out on the ends very similar to that of small herbaceous plants.

No manure in a container planting mix :-) It (and regular compost) compact/collapse too easily, impacting good drainage, which is critical in a container situation and crucial to the healthy growth of JM's. Chicken manure also tends towards alkalinity (and with a rather high salt content), so not a product/amendment favored by Japanese maples.

Local nurseries often carry acid planting mixes with a high percentage of a barky component. These make very good potting soils for containerized maples (as well as any conifers or most broadleaved evergreens). Or you want a very textural, gritty mix with a high concentration of bark, as well as drainage enhancers like perlite, pumice or Turface.

And with container plantings, it is much better to rely on supplemental fertilization periodically during the growing season rather than rely on the nutrients offered by any organic matter, like the chicken manure. There are just insufficient levels of microbial life in a container growing setting to be able to rely on organic matter or organic ferts to supply needed nutrients. Plus the fact that manures and composts are just not advised for container soil mixes.

Personally, I'd repot ASAP in a better suited soil mix.

Thanks for the responses. I am going to dig it up this am and take a look at the roots to see if there has been ANY growth. I have more good soil to repot. This tree is the focal point of the patio so I want one that is happy. I'll report my findings later.

I dug up the JM and the roots don't look happy. Most of them are brownish with only a very few white, new roots. Almost nothing was happening down there. I've planted the JM in an area where it is not such a focal point and tomorrow, I'm buying a new one from a top notch nursery. I've got the pot ready with much better soil. Once again, I appreciate the responses.