HRDad

Internet helpers I am at a loss.... 3 year old spa. Noted heater had stopped working due to insufficient flow fault. Then visually noticed water not pulling from tub down through filter, nor any flow back into tub from circ pump return. Have since then: 1) Confirmed no blockages in lines from tub to pump or pump back to tub 2) Circ pump and impeller spin and appear to pump water if removed and run separate from tub plumbing 3) Confirmed that pump was bled of any air What the heck is left to try/rule out?? THX!