ASDM 7.18 is Java-based. Modern browsers (Chrome, Edge, Firefox) block Java applets. Use these proven workarounds:
In the "Download Software" section, type "ASA" into the search bar. Select "Adaptive Security Appliance (ASA) Software" from the dropdown. cisco asdm 7.18 download
Use icedtea-netx:
sudo apt install icedtea-netx # Debian/Ubuntu
javaws https://<ASA-IP>/admin/launch.jnlp