New sand filter but extremely high pressures

I just installed a new Hayward sand filter but the pressure valve reads an extremely high pressure. With low flow into the pool. What is the problem.

We just opened our pool. Same problem. Low flow through jets into pool but high pressure reading in filter. New filter, new pressure gauge. Could it be a blockage in lines from filter back to pool.  All jets have the same low flow. Had local pool people come out. They had no answers.