A/C display is blinking...unable to recharge system

my AC hasn't worked for a couple of years now...but it's gotten into the 100's this week so i decided to try and give it a charge...problem is...i can't charge it...the pressure gauge on my line from the refrigerant can is reading in the red...i know there is nothing in the system because i replaced the compressor last year because the clutch assembly on it fell off...the fuse to the compressor is fine...but on the dash of my air controller in the cab "A/C" is flashing...it's never done this before!!!
what is that telling me?

how can i get the 134 into my system...and yes i know it's going into the low pressure side...

when you pumped it down did it hold a vaccum?

yes it did