Audio trouble

So last night everything was working fine, but this morning I started up the truck and after driving down the street realized my sub wasn’t working. Also sounded like my speaker amp wasn’t either.
After I get home I check everything out and the speaker amp indeed is not working. The sub amp is working, but the sub isn’t. Very confused as what could have happened overnight to stop the speaker amp from working and don’t understand why the sub isn’t if the sub amp is running fine.

 

What sub is it?
Step 1-
Push in and out on the sub to see if it moves in and out or it it’s seized up or feels gritty/scratchy (it should move smoothly)

Step 2-
Grab a multi-meter if you have one, set it to AC volts, and meter the speaker connection on the amp to see if it is outputting audio