I attempted to Pause the Standard Shield, but accidentally Stopped it, now it’s not listed under Resume Providers, and I have no idea where to look to turn it back on. Whereabouts should I look?
Go to “on access protection control” and restart it from the menu there for Standard Shield.
ah, thank you.
Glad that helped. Welcome to the forum. 
The Resume option is normally for those providers that you have ‘paused’ so I’m not to surprised it didn’t appear or rather the Resume option would have been greyed out.
You effectively have to do as sded mentioned, or if all failed you could always reboot as that should have restart stopped providers.