AFL 30GHR hydraulic pump not pressing completely

As the title says I'm having the same issue with two press motors (both AFL 30GHRs). They will advance the head until it makes contact with the fitting, compress it about a quarter of the way, then stop advancing without making the "pop" that I'd typically hear when the pump has reached 10,000psi. I got through two fittings just fine this morning, although the second one went pretty slow. I've tried using a different head and different hoses, I've got good clean hydraulic oil, and it's not leaking from anywhere. I use these press motors pretty often and never had this problem. Just wondering if anyone on here has encountered a similar issue, and if there's a known solution or workaround. Thanks in advance