I could not get fluid to come out of the bleeder valve

I tried to bleed my clutch and no matter how much pressure I put into the line I could not get fluid to come out of the bleeder valve. Fluid would come out of the slave cylinder input/supply line fitting. So it appears that it’s just not passing through the slave cylinder, if it’s even getting that far. I have heard there’s a safety valve of some sort at the end of the supply line that goes into the slave cylinder that I need to reopen since I just did a motor swap and it shuts itself to keep the line closed. Any help would be appreciated.