Fuse is blown.
Go to JD web page, click support, dial in your numbers and read the manual ( you can not download it but can print it out in sections ) find your wiring diagram and check.
JD use either a fuse or a fuseable link.
Fuses are easy, fuseable links are a length of light wire that melts out same as a fuse but a right royal Bast? to find and replace.
Check the big red wire from the battery to the starter solenoid.
All of the mowers power comes off this wire at the hot solenoid terminal.