Bluegrass is just slow--worse yet--the low temps--it would be faster at 85 degrees. Bluegrass is best used as sod--unless you have control of irrigation. And no doubt your customer did not water on days when it did not rain. It looks to me like he did not water last year. Probably all that you can see out there, is perennial ryegrass. For best results...sell a spring seeding together with a fall seeding. Slit seeder penetrates the thatch. Take precautions so you get paid--take the check on the spot if you can.
Perhaps this is a good spot for tall fescue sod--if not there already. Tall fescue of the lateral spread type (Titanium LS) mixed with 10 percent bluegrass would give it the ability to repair itself after a hot spell. It is difficult to get new seed to germinate on top of old thick thatch--what type of soil preparation did you use? Did you omit crabgrass control?
What seed mixture?
Bluegrass is just so slow...
I don't think fert has much to do with germination of seed...just stimulates growth afterwards.