The 698 replaced both the 598 and 798 and has the same sonar/GPS/mapping capabilites, just a poorer display for Side Imaging since it is narrow.
Settings are the same. The unit should automatically read the Lakemaster card when inserted.
Check the main Chart Menu to see if you have a Chart Select setting that needs to be changed.
You should have that setting whether you have User Mode set to Normal or Advanced.
If that doesn't work, you have a faulty card reader if you haven't damaged your map card.
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1