Wire in breaker panel is dead
Now we know the power is good at the breaker.
Trace the black wire back to where it comes in the panel.
Follow the white wire that the black comes in with to the grounded buss make sure the wire is not broken and is connected to the buss.
Next go to the first receptacle pull it out. Check for voltage, that wire splice looks small to me like 14 awg if back stabs were used the failure is at the last working receptacle or first non working (once the splice is put together).
If that is the first receptacle between the panel and that receptacle the wire is broken and needs to be replaced.
Remember to check the other side of the wall I have been called many times to fix circuits where the problem was a GFCI in another room almost exactly opposite from the dead receptacle.