Why is Coinbase not letting me buy?

I've been trying to make a purchase on Coinbase, but I'm encountering some difficulties. The platform seems to be blocking my transactions, and I'm not sure why. I've checked my account balance, and I have enough funds to cover the purchase. I've also verified my identity and completed all the necessary steps to set up my account. Yet, I'm still unable to complete my transaction. I'm starting to worry that there's an issue with my account or Coinbase's system. Could you please explain why Coinbase is not letting me buy? I'd appreciate any insight or suggestions you have to resolve this issue.