cant use my purchased purchased premium credits after my premium subscription expired.

idk if this is a bug but i bought $8 premium credits on top of my subscription to get 100 more messages. now my subscription is expired and i still have 10 credits remaining out of my extra 100 messages that were supposed to never expire but i cannot use them anymore. on the chat screen, it says that i need a premium subscription to use claude 3.7 even when i have 10 premium credits left. is this intentional? or is this a bug?