Make sure the battery is fully charged and check the connections.Try bypassing the starter solenoid with a heavy jumper wire, if it cranks the solenoid has gone on vacation or there is a wiring/interlock problem.

Checked the battery and it is fully charged, the connections are tight too.

Anyway you can give me a little more guidance on how to bypass the solenoid...I'll be honest, I think I am fairly handy although I am lost here.

Thanks!

Trace the positive cable (the red one) from the battery to the mechanism the cable is connected to. That is the solenoid. Near that connection point there will be another connector with a cable that goes to the starter. Jump between those two connectors. If still nothing, you could have a keyswitch problem or a safety interlock problem; you'll need a multimeter to check those out.

"Checking the connections" is not simply putting a wrench on the cable bolts on the battery. It entails tracing each cable (positive and negative) from the battery posts to the other end of each cable to its other end attaching point. Typically, the positive cable will end at the starting solenoid. The negative cable will end at the tractor frame or the tractor engine block.
Checking the "far ends" of the cables includes putting a tool on the bolt that holds the cable in place and testing it to see if it turns in either direction and that the cable does not move freely around the bolt (the bolt can be corroded and seized tight, while the cable end terminal is actually "loose".
As a precaution (and this is very important) always disconnect the battery negative cable from the battery before you put tools to any of the other cable attaching points on the tractor. And when disconnecting the battery for any reason, remove and reconnect the cables in this order: Disconnect the negative cable first, after the negative cable is loose and moved away, then disconnect the positive cable.
When connecting the battery cables, attach the positive cable first, after the positive cable is secured, then attach the negative cable.

When checking the cables for good connections, you must check the cable that runs from the starting solenoid to the starter to make sure its terminals are secure too.
The detail about it having gotten wet in the rain could still have some significance. Electricity and water do mix, contrary to popular lore. The problem is that when you mix them you often get corrosion inside switches and connectors that shows up long after the initial wetting event.

There are several components in the electrical system that might suffer failure after being exposed to a drenching rain (or even a misguided wash job).

Below is a stock test procedure I have written for testing testing a typical LT/GT starter controls system.
It was written with Craftsman in mind, but it is generic enough to apply to most modern OPE.

Attention Walt Conner! If you have read this far.....turn off your computer now.

Here is the test outline:
For this, a 12 volt test light will probably be easier to use than a volt meter. So that's how I will describe the tests. The battery must be fully charged for these tests to be accurate and you must make sure there are no blown fuses. Clip the ground of the test light lead to a known good ground, negative post of battery is ok. Confirm the test light works by touching the probe of the light to the battery positive post. If light works, proceed to tests. You might want/need a helper to turn the key switch if you have short arms.
Lock the brake pedal and make sure the PTO switch or, or other engaging method is not engaged.
Step 1 Find the "S" terminal on the back of the key switch (a white wire). Insert the probe of the test light inside the wire connector where the white wire enters the connector, make certain the probe is deep enough to touch the metal terminal. Turn the key to the START position. The test light should burn. If test light does not burn, replace the key switch.
If light burns, go to step 2.
Step 2 Touch the probe of the test light to the small white wire on the starter solenoid, turn the key switch to the START position. If the test light burns, the entire control circuit for the starter solenoid is good. If this is the case, move the test light probe over to the large post on the solenoid that has the cable going to the starter. Turn the key switch to START position. If the test light burns now, the starter is faulty, or the cable from solenoid to starter is defective. If the test light does not burn now, the solenoid is faulty.
If the first test of the white wire on the solenoid did not cause the test light to burn, go to step 3.
Step 3 Find the brake switch and locate the 2 white wires on that switch (there might be 4 wires on the switch, only check the white wires). Turn the key switch to START and hold it in that position. Touch the probe to each white wire. If the test light burns when touched to both wires (one wire at a time of course), the clutch/brake switch is good. This would mean there is an open in the white wire circuit between the brake switch and the PTO switch (the switch on the deck, because you have power on the white wire leaving the brake switch but no power on the same white wire arriving at the solenoid).
If you have power showing on just one white wire at the brake switch (with pedal locked down), make sure that the switch is adjusted properly. If adjusting the mounting of the switch does not give power to both wires, replace the brake switch.
Now, if you have power at both of the white wires on the brake switch , move on to the PTO switch in step 4.

Step 4 Find the white wires on the PTO switch and place the probe on the white wires (one at a time). Turn the key to START. The test light should burn on both white wires. If only one white wire has no power on it when in START position, replace the PTO switch. If you have power on both wires here, but not at the starter solenoid, there is a break in the wire between the PTO switch and the starter solenoid.

Good instructions mownie. I'd sure start with checking the fuses on that one. Good luck strong back.
Dayton

Mownie is good and knows his stuff. We're lucky to have someone like him on this board.