You have to wait. Usually in terms of years.

First year they sleep.
Second year they creep.
Third year they leap.

Digging up or disturbing the root system of a hosta will only start you over from the beginning of the waiting period. Hosta do not grow fast like annual flowers for instant gratification. If you want to start off with a larger plant you have to buy a multi-eyed plant grown in a pot or buy multiple single eyed plants and put them all together as one.

Can't tell if it's planted too deep without a picture. If you got your "mature division" from Hosta's Direct, there's your answer. They specialize in miniscule plants. You know how to make them grow. Lots of water, a bit of sun, and appropriate amount of fert. Or better yet go buy a larger one from a better nursery. That's what I intend to do with my LS Paisley Print from HD.

Steve

Steve, you guessed it! lolol I didn't want to mention names but bingo! That explains it! Miniscule hostas is right!

Well, I will give it more time but I thought I remembered Ken saying that they can sometimes be lifted and planted shallow to help the growth if planted too deep.

I'll have to search Ken's brilliant posts lol!

This is a previous post from ken...credit goes to ken_adrian

hosta that are out of the orinarily slow may be planted too deep .... dig up the whole root ball .... heave it as high as you can ... right back into the same hole .... and make sure the top of the crown is right at ground level .... it will take off like a rocket ... or you will find out it is dead ...
the near death experience is said to trigger hormone release.... a growth stimulant ...

banyai told me [pauline of gold standard fame's son] that he would scrape puny hosta across cement to scar the roots ... thereby stimulating it ...

he walked around my yard one summer and pointed to 20 hosta that were underperforming ... and told me they were all planted too deep ...

he was right ... lift them up .. and they will take off ... do NOT be gentle ...

Contributed by ken_adrian

I think that you did not get a mature division as Steve intimates. My 'Risky Business' multiplied quickly.

With respect to the one in a pot...Hostas are DIFFERENT in pots. Repot your potted one in a pot that just contains the roots. When the roots grow out of the drain holes, up pot it up ONE size. Otherwise, roots will rot, trust me, I found out the hard way and lost a bunch. You don't need to disturb the roots when you pot it up to the next size pot. Just take that formed root mass and plop it into a pot about 2" greater in diameter.

-Babka

I just noticed my Risky Business has a solid green leaf, does this one revert easily?

Just an update: I lifted the one Risky Business that was in the pot. I needed to see what the heck was going on.

The rootsystem was tiny! No wonder it wouldn't grow well. I lifted and made sure to plant higher. I also incorporated some compost/composted manure blend into the pot. We'll see how it goes. If it doesn't do well I will go to a better vendor (I can think of a couple off the top of my head like Hallsons :) or New Hampshire hostas.