when u fitted the calipers did u put them on the correct sides so that the bleed nipples are at the top?

if this is correct and ur still on normal flexi hoses clamp the all up with properbrake hose clamps if the pedal is then solid, remove them 1 at a time checking the pedal pressure, as soon as u remove 1 and the pedal pressure goes bad again thats the corner ur fault is at

If you can't get good pressure with all 4 hoses clamped then theres a fair chance your master cylinder is goosed