users upgrading to premium membership are not being charged!

This is a huge issue, on a freshly launched live site, where an existing membership of 800 are being asked to upgrade to a paid account.

The site has 2 subscriptions: 1. free (finite 1 year) 1. Paid (serial 1 year $48) both are active and public.

The site is using the paypal solo gateway and all users are already set up as free members on the paypal solo gateway.

If a "free" subscription user goes to the renewform page they see an option to "upgrade", but when they click it, they are not asked to pay!

newly registered users who choose the premium option are properly brought to paypal.

Any ideas?