An issue with the sonar viewer display has been raised, where the sonar is not displayed when the sonar viewer is opened. This is a problem with the relative sizing of the channel displays, and there is a simple workaround. The issue only arises when opening logs with only the primary and down-scan channels selected, and the workaround is to de-select both of the visible channels (primary and DS) and then re-select them. This will force the channel sizing to be refreshed and you shouldn't have any problems thereafter - although you may need to repeat the process every time you open the viewer. We'll include a fix for this in the next maintenance release.
Top image shows sonar viewer when first opened - the channel displays are actually squashed to the left. Click the channel buttons at the bottom twice to force a resize.