Hello DJTDiesel,
If the songs are showing an exclamation mark next to it, that would mean it is unable to find the actual file for that item. To start, you'll want to make sure those songs are playing on the computer. If the songs show an exclamation mark on the computer when trying to play, then you'll have to work on re-importing them into the iTunes library first before you can properly sync them to the phone.
If the songs are working on the computer, then something may have gone wrong during the sync process to the phone and you'll want to remove and start over.
In iTunes on the device page, select the Music option in the sidebar on the left then uncheck the Sync Music option and select Apply. This will remove whatever music was on the phone. Once that finishes, re-check the Sync Music option and select Apply. This will begin the process of syncing the music over again. If you're syncing somewhere around 15k songs, this will most likely be a multi-hour process to complete. Make sure the device remains connected to the computer until the sync has completed. If it is disconnected before the sync has finished, you may run into songs displaying the exclamation point again.
Use iTunes to sync your iPhone, iPad, or iPod with your computer
Cheers!
