DR Power TB2 44" blade (Tow Behind Mower) Won't Start

Hi everyone!  I am new to the forums and joined primarily because I am having a heck of a time trying to get a DR Power Tow Behind mower I recently purchased (used) to start. I'm not super knowledgeable with small engines, so part of this repair job is trying to get more comfortable with the repair and diagnosing the issue to fix it...  Here is the breakdown:
 
Bought the user TB2 44" tow behind knowing it wasn't starting. I was under the impression it needed a battery and an air filter.
Once I got the thing home, I did the following:
 
1. Replaced Battery
2. Replaced Air Filter
3. Replaced Spark Plug
4. Added new fuel
5. Checked the fuses - both look great
6. Cleaned some of the electrical connections that looked a bit dirty or corroded.
 
Well, after those steps, I turn the key and I get nothing, not a sound. No starter or solenoid or any noise.  Just nothing.
 
We checked and the Solenoid and the Starter Motor are both receiving power.
 
I spoke with DR Power today and they noted that it could be the key/ignition assembly. I purchased one just to at least rule that out as being the issue.  They noted that even with a bad ignition assembly the power would be still be passing to the starter or solenoid. 
 
While I wait for the key ignition assembly to arrive, I took the current one apart and the plugs etc. looked ok. I went ahead and cleaned it up to ensure there was no corroding and applied some electrical cleaner to it. Not sure that it will do much if the issue is internal with the ignition assembly, but worth a try.
 
At this point I am mystified as to what else could possibly be causing, well, nothing to happen when the key is turned lol.
 
 My thoughts:
1. Possibly a faulty wire in the wiring harness? My next job is going to be to trace all the wires to see if any are not powered.
2. Starter is bad or locked up inside?  (I do think that this was stored outside for awhile)
3. Perhaps the  solenoid?  I think that this is probably a long shot though?
 
Any thoughts or ideas?
 
Thank you in advance!

This has a 16.5 HP briggs and Stratton. I haven't checked to see if it turns as it was noted it worked and had a battery issue... erg.  I'll try later today when I get back.