Again a vital clue that was not made available
So meter comes on = fuse is good & switch is getting power
You have a wiring problem
One of the safety switches in the cranking circuit has failed or the wire are broken or the seat switch plug is loose
Seat switch is easy so unplug it then replug it and make sure it is fully home some have a shorting strip to prevent you using the mower with the seat switch unplugged or bypassed .
The actual cranking circuit is a daisy chain
Power in wire to key switch to starter terminal
PTO switch ( in off position )
parking brake
Solenoid trigger
ground
Your wiring diagram is in the parts book
The parts book is a free download from Husqvarna
That will give you the correct colour wires to test
Pull the sockets off the back of the plugs & bypass each switch one at a time starting from the key
When the engine suddenly rotates you have found the guilty party
If you get to the solenoid trigger wire and you still have battery voltage then that leaves the ground connection to the solenoid ( can be the body or a thin wire ) or the solenoid itself or the wires between the plugs .
You test the solenoid by jumping from the hot terminal on the top to the trigger terminal on the bottom ( remember the round connection )
The engine should crank if the solenoid & starter is good.
Otherwise you then go and jump between the individual plugs to find the broken wire / bad connection .
