those clutch master cylinders are a p.i.t.a. to get the air trapped in the pumping seal area out of... I disassembled mine once, for examination... and had to end up "reverse" bleeding the system... That does work, but is messy and somewhat tricky to perform...
You end up using an "inverted" container with a subsequent amount of fluid in it to supply, and a hose attached to the slave bleeder valve.... Then, crack the slave bleeder, and "suck" the fluid up to the master cylinder bleeder, using a mity vac.. It helps to have 2 people, one to hold the container and crack and reseaql the bleeder on the slave, and you can crack the bleeder and draw vacume, and reseal the top bleeder.. I have done this myself, and it does work great, as the air is trapped up top... so trying to force it downwards is a lot more effort, than drawing fluid upwards.. just reseal the top bleeder end bottom one every cycle... and keep a good vacume on the line before breaking the top one open.
Also, using small zip-tie wraps on both hoses, cinched up tight, really helps prevent 'accidents"...
Once the air is sucked from the top, the piston in the master will work, and pump fluid...