Forced to add debit/credit card to complete purchase

[AcruzMx]

I just had a deposit from  merchant mequedouno.com.mx and kept the money in a new PayPal account

When I tried to do a new purchase to the same merchant, I was not offered the chance to pay with that very same money, but asked to use again mi debit card. 

Why is that I can't use the money I left in my PayPal account?

I went trough a post dated July 2011 with the subject above, and the explanation there does not suffice, for I was asked for the card payment and was never offered at all any other option.

Thanks in advance

[bjc4200]

I have the same problem several times and still can't find an answer.  PayPal says I should have a payment option at checkout but I'm not given the option, it just charges my credit card.