OK your mower won't start
And it is branded Cub Cadet
The Deck is 54" which has nothing to do with anything but thanks for sharing
So that narrows it down to around 300 combinations of mowers & engines.
Can you please provide the model number of your cub and the make & model of the engine.
Funny enough the different engines are wired differently .
It sort of makes it next to impossible to offer you any assistance when all we have to go on are the words you typed on the screen
Thus the only thing I can tell is you impulsively went out and paid a lot of money to replace a starter which you did not bother to test and then even more of a solenoid so I will hazard a guess you have a briggs engine cause most of the Kohler & Kawasakis use piggy back solenoids, although it could be an Onan if the mower is old enough.