It's possible the panel you have illustrated is one of several such panels serving power into the unit, so you may need to do an exhaustive search for any others.
It complicates things if this building has more than one unit. Wiring to the other units could be still energized obviously... And this could create false readings on test equipment (capacitive coupling) -- or there could be actual cross-connection between the units, so your unit might not be fully de-energized unless others are too.
Cross-connection could be a load in your unit served out of their circuit... Or even a neutral cross, where their load is served from their panel, but it uses the neutral on your panel, and if you sever that neutral wire which has current flowing through it, the upstream side will be energized to 230V.
A lot of testers are complete junk, or are not made for house wiring and need some skill to successfully apply.
A common night light is surprisingly useful. It is simple, honest and not particularly reliable, which means you must check and double-check it. I honestly find them more useful than 3-lamp testers, though those are OK for a final check for new outlets.
Plain old analog voltmeters with the moving needle are useful.
Digital voltmeters (DVM) are useful but a little tricky. They are so sensitive they can pick up micro-currents from capacitive coupling, which happens when a dead wire runs physically parallel to a still-energized wire. So you have a DVM a reading of 109 volts on a 120V circuit that you thought was turned off - plug a night-light in, and the voltage mysteriously disappears.
If the electricity is powerful enough to illuminate any light, even an indicator light -- that's not capacitive coupling, that's genuine power.
Ah, the "magic 8-ball" testers.
The legends are useless. Hot ground reverse suggests it is seeing power between hot and neutral, and neutral and ground. Nothing says the voltage is 120V. For lack of a neutral, HN and NG lamps were in series seeing 60V each. This was a lost neutral. Hot and neutral were never reversed. I hope you did not reverse them in an effort to clear this message!
A hot-neutral reversed combined with a lost neutral would also read "correct" and yet not work.
Best Answer
Most likely scenario: your main has a connection to the bus inside of the panel that distributes the power to all of the other feeder breakers. That connection is likely bad / corroded / burned, something that is creating high resistance. With no lod, your tick tracer picks up that there is voltage present, but as soon as you apply a load to it, the resistance causes the voltage to drop to effectively zero. Resetting the main breaker wiggles it a little to make just enough of a connection to satisfy that tick tracer, but that's it.
This is your life and safety involved here, the next phase of development of this problem may be a fire. you need to call an electrician.