After many recommendations, I've been using SSS, but after two days its not hard/set...

any ideas? is this typical?

Deffo not normal, it usually sets in 10-15 minutes and cures fully over a 24 hour period.

then what am i doing wrong?

put SSS on bracket, then pushed mudguard onto it

pressure with g- clamp overnight

i didnt wait after i put the SSS on the bracket, just plonked the mudguard straight onn....