Hello

It looks like the error is generated on PayPal end. May be you have some problems with your PayPal account. Try to contact with PayPal support.

The possibility to use 'any other method' depends on the product's vendor. If you don't see any other methods in shopping cart then you may try to contact with the vendor. May be he can accept payment using some method which isn't available in the Market here. In this case the license for you would be processes manualy.

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Best Regards
Anton