Would Device Manager Version 7.1(5) currently used with an ASA5520 on 8.4(7)30 work with the ASA5520 on 9.1.7.23?
This document gives the impression any ASDM 7.1.x is still compatible with ASA 9.1.x:
https://www.cisco.com/c/en/us/td/docs/security/asa/compatibility/asa-vpn-compatibility.pdf
This other document gives the impression ASDM 7.5(2)+ may be required for 9.1.7.23 compatibility:
https://www.cisco.com/c/en/us/td/docs/security/asa/compatibility/asamatrx.html#pgfId-112283