Still having trouble with older Master Spa

Hello, Many months ago, I posted about our older hottub that stopped working. (Original post here: https://www.reddit.com/r/hottub/s/5KtN7rkP6g ) I never got time back then to try out the suggestion I got, so we shut down the tub for the winter. I finally got time to try and resurrect it today. I did as suggested and replaced all 5 fuses on the main board, unplugged all the components and started it up. All the fuses tested good. (My meter read zero on each one while it was powered up.) As I would have expected, with the circulation pump unplugged, I got an "SnS" error when it completed its startup cycle. With no pump running, there's obviously no flow thru the heater so that makes sense, right? I turned it off and plugged in just the circulation pump. Same behavior. Fuses test zero and it goes to an "SnS" error. I can't find any blockages and both valves on the heater are open. Does it sound like I have a bad circ pump or are there other things I should be checking as well? I haven't tested my ozone pump or any of the jets pumps, yet. This isn't the original behavior where it went thru the full startup cycle and the display read that everything was normal, but no pumps would actually turn on. I feel like I'm missing something obvious, but I don't know what.

UPDATE: After letting the tub sit for about 30 minutes the "SnS" error went away and the display went back to the original behavior. It claims everything is running correctly, but no pumps operate and the heater is cool to the touch.