re: Getting Cell Signal and Wifi To Detached Shop

If your phone doesn't pick up the wifi inside the shop, neither will the mesh point. You could try getting another point and put it inside the house (or maybe under covered outdoor space) near the shop where the signal is decent. Your other options:

1. Powerline adapters
Easy and cheap
May work great
May work shitty
May not work at all

2. Run ethernet cable
Best option
Should have done while building
May be a pain or impossible at this point, or may cost a lot

3. Wireless bridge (many options available)
Cheaper and easier than running cable in many cases
Very solid, very fast (though not as fast as hard wire)
Usually relatively small and not offensive looking, but it will still be shite hanging on your house/shop