There are several reasons for this to come up. Sometimes resetting it from Nayax Core will fix it, sometimes you need to reload the parameters. If those don't work, call support and they'll get it back online. Their support has been very good the last few times I have called
Again, it depends on the state. Utah does not require licensing for small trailers but, surrounding states do. If you are stopped in one of these states, cops will usually just let it go if your vehicle is registered in Utah.
Depends on the states you are traveling through. Easiest is to get a temporary tag from your home state and comply with their laws. If it is owned by your wash, they could classify it as a commercial vehicle and then you have to comply with the commercial vehicle code. Put it in your name.
Looks absolutely matter. You can probably update your meter boxes without replacing. I would absolutely add the ability to accept chip and tap. A good facelift can do a lot for you. Consider updating your lighting if you haven't already, make sure the place is nice and bright.