Back in the 6.680 version software it stated in the release notes:
“These software updates draw a line in the sand. Once a user updates one or more of their units to software version 6.640 or 6.680 they must update all of the other Ethernet networked units to the same release. If they try to use one unit with software version 6.680 and another unit on the same network that might be at 6.610 or lower these models will no longer talk to each other until the unit that is at 6.610 or lower has been updated to the newest release of 6.640 or 6.680. If the units are not networked, this issue is irrelevant. But we always recommend that the user update with the latest code.”
All software versions after 6.680 will have these same changes. So if you update your 898 to the 6.740 software you will also have to update your 998 unit to the current software (which is also 6.740) if you want them to communicate via the Ethernet connection.

