Take a look at the video I posted on your thread. From either underneath the truck or from the wheel well, you can get a look at the main electrical connection to the starter. Pull the plastic cover off and see if the connection is tight. If it is, I'd just pull the starter and see what the contacts look like. Like someone mentioned, maybe for some weird reason the contacts and plunger in the solenoid weren't replaced when they did the starter work. The clicking sound when you try to turn over the engine is a classic sign it's a starter problem. If the contacts look good, maybe the starter just finally bit the dust and you need to get another one.
You will learn that even though your starter was supposedly professionally rebuilt, these supposed professionals often do a shitty job. Spend enough time on this forum and you will learn that us DIY mechanics quite often do a better job than the guys getting paid to do it on a daily basis. Why does this happen so frequently? Well, we're not in a rush to get the next job so we take our time and do it right. And, quite often, we know more than the paid mechanic because we've researched the job well and have learned from others who have shared information on forums like this and on YouTube.
I show you everything you need to get the starter out but it's still kind of a pain in the butt. If you have a friend with car mechanic experience, buy him some beers and get him to help you out.