@dfischer I have done more testing and cannot figure out what is happening.  If I set up the Deco with the ethernet cable to the shop plugged into one of the two bottom ports on the Deco, AND if I have my Tenda Router in the shop set to be an AP, then I get nothing at the shop.  If I remove the Tenda and plug the shop end of the ethernet directly into my computer, I get nothing.  Under each of those setups, when I look at my Deco app, the Tenda nor the shop computer show up as one of the devices on  the network.

But, if I plug in a router at the Deco using the bottom port, and then tie the Ethernet into the router, then my shop router DOES get the signal.  But, that means I have to have the router at the Deco running along with the Deco which I do not think is a good thing.  But, that is the ONL way I have found that gets internet down to the shop.  Also, in this setup, my Deco app does not show the shop router.  I would not expect it to, but it does show the router at the Deco as being in the network.

Setting up my router at the shop as an AP seems to make no difference.  It still produces the same wifi network in the shop as when it was a standard router. My login at the shop is the same login under either set up.  I thought it would have to be different. Under the AP, I thought I would have to be logging in using the house router SSID and PW.  Does not make sense.