Sylla

I was using a pyrometer* from the start.
Early on, I was setting cone packs in front of the peep holes. I'd look at the cone packs as the kiln reached target temperature. Painted lines of iron oxide wash on the cones helped; the cones can be difficult to see when everything is orange/yellow hot!
Be absolutely sure to acquire the proper kiln glasses to protect against damaging rays and any flying bits.
As experience grew, I became more dependent on my notes and the pyrometer readings, and less dependent on watching cone packs during firing.
I'm still placing cone packs on each shelf, however, I look at them afterward.
The potter I bought the manual kiln from fired their cone 5/6 clay to a "soft" cone 7, so, I did the same, which was way too much heat work for the red clay I was using.
Now I'm using clays that mature at cone 5, so that's what I shoot for, a solid cone 5, which typically meant the middle shelves bend the 6 cone a bit.
I believe you can expect the sitter cone to bend before the witness cone(s) of the same number do.
For what it's worth, I was setting the sitter timer and the drop switch up just in case something dreadfully distracting occurred whist firing; I never depended on the sitter, instead, was watching the pyrometer, the time, and the cones.
I've learned a lot the hard way, and everything noted above, I'd read about in this Forum!
...even so, I still "had to" make my own mistakes.
Next up, brand new numerically controlled modern kiln with "zone control"!
...very much planning set up and watch cones through the peeps, starting out, for the kiln's pyrometers may be a bit off.
*Dual Input Pyrometer - Kilns | Ceramic Pottery Kiln, Glass Kiln, Pottery Wheels | Skutt

The cone in the Sitter should be bent to 90 degrees. If it's less than that then you need to adjust the Sitter.

If the timer shut it off before the cone dropped, then it didn't reach temp. Turn the kiln on high for a few minutes and see if all the elements glow. If one is out, then it's probably just a fried element. If two in the same section are out, then you probably have a bad switch. Or in both cases it could be a wiring connection fried out somewhere, which should be easy to see when you open up the control box (with the kiln unplugged). If they all glow, then they're probably worn and need to be replaced. Post a pic of the elements so we can see their condition.

Things that may help:
Kiln glasses - to protect your eyes from harmful rays and any flying bits - so you can watch witness cones through the peep hole(s). Cones tell the story!
Pyrometer - once you've dialed in your schedule(s), you may just watch the pyrometer, then check your witness cones afterward.
Powered kiln vent - moving a tiny stream of air through the kiln a) provides oxygen, b) helps keep the amount of yucky fumes down, and c) helps your kiln last
Testing! It might take a few runs to get dialed in - each clay (and glaze) may present a different challenge.
Notebook - take notes! It can be hard to remember what worked after a few years...
 
My first kiln was fully manual - three high/medium/low switches and a "kiln sitter" (which had a timer and a drop switch that would actuate when the small cone, or bar, melts).
For bisque firing, I'd run the kiln up to about 200F the night before - thinking that by the next morning, all would be very dry.
From there, I ran on high up to my target (1950F), with a half hour hold at 1500F.
For glaze firing, I'd run up to target temp (cone 5) on high, drop 100F, hold there for half hour, then set all on low for a slow cool to 1850F afore turning everything off, including the kiln fan.
 
I'm holding at 1500F for the bisque fire on account of I'd found the red clay (and to a lesser extent, brown and buff clays) behaves better when it gets a longer cook. My guess it's the larger off-gassing bits that get burned out better with more time.
I'm dropping and holding, then slow cooling for the glaze fire because it seems to help with "healing over" glaze defects.
 
Hope that helps!
A fully manual kiln requires some attention. That said, perhaps your kiln has a controller? lol!
Any road, be safe.