Help, I know this subject has been brought up before but,
I'm trying to refill my shimano brakes back up.
I'm using the syringe from the bottom up method. I've read most of the online instructions and also the ones of the shimano website.
The bleed nipple is free from dirt (another problem I also found on the forum)
The hose isn't blocked as fluid comes out when the brake lever is pulled.
But I still can't get the fluid up into the reservoir from the caliper.
Any ideas please?

Make sure you are undoing the calliper bleed nut enough. Mine needs more than the quarter turn from tight the manual suggests (more like a whole turn).

It will drain top down with it only partially open but bottom up is nigh on impossible for some reason.

What fluid are you using?

Using Mineral oil as normal, not shimano branded though.
Have had bleed nipple undone way past the recomended quarter turn.