Your post was basically blank @jiabaow5192 so there's not much to go on in just the subject line.
If you want assistance from the Community Forum then you need to explain/describe your issue clearly.
E.g. what happens when you try to top up (buy a membership plan I presume?) here?
Any error messages?
When were you last able to successfully buy a membership plan?
Is your payment card still valid, not frozen via your online banking, and there are sufficient funds in the account if it's a debit card?
If you need to contact 48 support about this then see the links in my signature below.
