Groups buying/selling land Question

I deeded all the mainland I had to my group which seemed no problem. Now I've sold about 2048 and the money went into the group. Today I attempted to buy land for the group and it says that the group does not have enough land credits.

What should I do? Is there some way to extract this money from the group?

These are 2 different questions.
1) No, you can't withdraw money from the group once it's paid. You'll have to wait until it's cleared through the LL account team. This may take days.
2) Did you click on the "remove tier donated to group" when you sold the land? If so, you'll have to re-donate tier into the group to be able to buy more land for the group. Check the Info for the group, Land tab. It will tell you how much land it has, how much tier you've donated into it, and how much more land you can buy towards it.

No I did not remove the tier donated to the group so then I just need to wait until this money clears I guess.

also you should know that the money will be distributed over all the members with the accounting 'abbility', so perhaps you must check your group roles !?

*sidenote: the remove donated land from group checkbox does not always work

a topic with step-by-step land selling hints;

You have to have the tier donated. Go to the Land and L tab in group info and see what it tells you about how much land tier is donated. If the allowed amount is smaller than what you're trying to buy (factoring in the 10% bonus), you are going to get that error.