hot water heater regenerating

So wondering to be sure on thermospyoning and gravity fed system. Ive got 2 water heaters that are different size. My plan was to just run loop back from the upstairs shower line being the highest and furthest away fixture. But i also have a toilet and vanity and wash machines on basement level...

Hey all, would love some other thoughts on this issue I'm having. I just installed a brand new 55gal State electric water heater in my shop (using it in radiant floor project). Wired it up, did the plumbing, tested circulating pump, all good. Turn on the power and... It won't regenerate...