Why my apple account balance cannot exceed 2000$

See If your payment method is declined in the App Store or iTunes Store https://support.apple.com/en-us/HT203005.

Also see: Fix ‘Your Payment Method Was Declined’ Error In App Store https://www.addictivetips.com/ios/fix-your-payment-method-was-declined-error-in-app-store/

If you need additional help, use this support link from the document https://support.apple.com/contact  or use:

Apple telephone support  for help in solving your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362 Be patient sometimes Apple support is closed to immediate phone support.

Apple Support Twitter https://twitter.com/AppleSupport There may be an hour or so wait.

iTunes worldwide support via text or chat using this link https://support.apple.com/choose-country-region/itunes After choosing your country, see the heading Tell us how we can help.

Contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call       

If necessary, try Twitter

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.

I don't know the answer to your question, which is why I suggested contacting iTunes Support. They may know the reason.

I am having this same problem. I would like to buy a new macbook but can't.