A common reason is a mismatch between the app store email and LastPass email. File a billing case and attach the Google Play receipt.
https://support.lastpass.com/s/document-item?bundleId=lastpass&topicId=LastPass/billing_report.html
https://support.lastpass.com/s/document-item?bundleId=lastpass&topicId=LastPass/FAQ_View_My_Cases.html