Splashtop is opening a small viewer window with a scaled-down remote screen

Once upon a time, when I opened a remote screen on my Mac's 27" monitor, Splashtop's viewer window was large enough to approximate the size of the remote screen, and the aspect ratio of the viewer window matched the remote screen.

Recently, Spashtop has been opening a small viewer window (800 x 696 pixels), with the remote screen centered.  Since the aspect ratios don't match, there are black bars above and below the remote screen.  This means at the start of each session I must enlarge Splashtop's window to enlarge the remote screen to a usable size.

Are others seeing this behavior?  Is there a way I can get Spashtop to automatically open a large viewer window?

I'm running Spashtop Business 3.7.0.0 on macOS Sonoma 14.5, and nearly all remote screens are Macs.