When I switch from say, 30 MHx down to 1 KHz, I sometimes do not get a trace until I push the autoscope function.
On an analog scope all I had to do was to change the time base dial.
Not a big deal now that I know what to do.
i suspect you are on "Normal" triggering mode (which is i suspect unavailable in CRO), you can change to "Auto" triggering mode and you still can see a flat horizontal line if signal is too slow. you can rest assured that we still have that time base dial on DSO to do the same...
CROs have both "Normal" & "Auto" trigger mode.
When I am looking at various points in a DUT, I normally let the 'scope "free run" in Auto.
Using DC coupling, with no vertical input voltage, I will then see a flat line at my selected zero position, .
This allows me to look at DC supply lines, as well as signal levels.
With 1v/div setting, if the line jumps up by around 5 divisions, I'm looking at a +5v supply, & so on.
If I then look at a point carrying signal, I will usually see that signal (unless it is very small), & can then adjust time/div, volts/div & trigger level to give me a stable display.
The early DSOs I played with didn't seem to have an equivalent to "free running", as without an input signal, they would not show a trace----it seems modern ones do.
I thought "roll" might do the trick, but touching the probe on a DC level displayed a transition from zero to that level, complete with contact bounce, (due to my shaky contact with the probe) overshoots, etc., which made it useless.
In most cases, it wasn't worth persevering with it, as there was a quite adequate CRO available.