i managed to get it working

for anyone else with a similar problem, the ps3 i got was on dex firmware but it was running in cex mode and i had no idea till i figured it out
if this is also the case for anyone else your gonna have to get your default_mp.self and make it an eboot using the self resigner tools (they are on NGU just google search it and the post has instructions) and use the eboot you make using the tutorial and the sprx should work

(hope this helps other new modders like me haha)