Hello @krysia,
Welcome to the community!
I will suggest to verify if you are following these steps: https://support.lastpass.com/s/document-item?language=en_US&bundleId=lastpass&topicId=LastPass/update-payment-method.html&_LANG=enus with the steps listed here you should be able to update your payment details.
Kind Regards,
Alejandra
LastPass Support