I have a Geo Thermal heating system with a 50 gal electric HWT which is assisted with the GEO unit. After we bought the house I found it to be really different that a gas water heating system especially with with a tank-less setup. So I run a 3/4" hot water loop with a pimp, works great. Hot water now, right away instead of waiting a very long time due the house being 85 ft long. NOW...since the wife wanted a Walk-In tub, that hot water sucks up 38 gal quickly and seems to not run hot for a full fill.
I bought another 50 gal EHWT and piped it in series but can not get water circulation now.
What a pain...so I had to go back to original setup until I get more information of schematic. So any drawings or advice would be greatly appreciated.

Did you install a check valve in the pump line? If not, start by installing a check valve and see if that resolves recirculation issue.

Also, did you install a means to purge air out of the recirculating line? If not, install a ball valve (black/yellow) and a draw off (red) right before the pump and purge the line clear of air...see image.

Attachment 49241

Doing both these things will definitely solve any issues you have with recirculating the water.

Mark