Hi there,
My company recently converted to an organization as well. It’s all been rather confusing, but this is what we have learned:
What happens when you convert is that the workspace becomes a TEAM in an ORGANIZATION. For whatever reason, (possibly a missed step during conversion, or just a program flaw,) our paid workspace turns into a PAID TEAM in a FREE ORGANIZATION. At that point, the teams are sort of treated separately. Only that one team will have the paid features, any new teams are essentially on the free plan. (I’m still not sure WHY that takes away the admin console. 
)
To fix it we had to have Asana sales support apply the paid plan over the whole organization. Once that happens all teams will be treated equally, the admin console should return and you’ll be able to manage things from there again. (Thus far I haven’t found a way around getting support to do it for you.)
NOTE: You’ll want to make sure the billing owner has added his/her domain email to their main Asana billing account. They are the only one who can request the change from support.
Hopefully this sheds some light on what might be causing your trouble, or steer you toward a possible solution. Or you might be experiencing a different issue. This is just our experience with the process. 
I hope they can help you get it sorted out soon!