I had an allowance for my son set up and for some reason it stopped. When I go to manage allowances it won't let me either activate or set up a new allowance for him

Hello harriskym,

Thanks for using Apple Support Communities.

To set up an iTunes Store allowance, please take a look at the following support article:

iTunes Store Allowance

http://support.apple.com/kb/HT2105

Take care,

Alex H.

This does not answer the OP's question at all... Clearly they knew how to set up an allowance because they HAD an allowance set up.