Pump will not draw air back in after a pump.topeak master blaster mini dx

You are most likely using the pump set up to work with a Schrader valve when you should be using it with the internals set up to work with a Presta valve. This video will help you identify the valve type and explain how to change the internals of the pump: http://www.topeak.com/pages/368/news/detail/832
This video will explain how to change a flat:http://www.topeak.com/pages/368/news/detail/830

I hope this helps, Eddie O - Topeak Inc

Try moving the little arm on the back to the down position. If that doesn't work then the pump may have threaded on. Righty tighty lefty loocey. If it still won't come off then you should take it to a bike shop. Do not use the pump again if it was not one of the first to issues.

There are several parts see photo , part 11 is reversed to accept the different valves ie: presta/ Schrader

Place over the valve - do not press on too far.
Flip lever up, away from the pump body, and start pumping.
When done, flip lever back down and remove. If difficult just carefully hit the pump underneath near the head with your palm. Unscrewing the head very slightly may make removal easier, but make sure there's still a good seal when pumping

I’m happy to help further over the phone at https://www.6ya.com/expert/donald_f2ed37026a3ac881

I have the DX, and I only use it for Presta valves. With mine, the lever is down to insert it onto the valve, and up for inflation. On yours, the head probably unscrews, and the black rubbery piece the grabs the (Schraeder) valve might be inserted wrong-side out. It's easy to remove this piece and put it back in the other way. This might be the problem. Be careful to do this over a clear area, as the pin in the pump might fall out. If it does, no big deal, just put it back in. Probably stating the obvious, but make sure the pump is seated on the valve stem all the way. Good luck!

i've just bought one, they seem pants, un screw the cap, theres a remove the rubber part, tap out the green bit, then just switch it round.

but i've tried pumping my tyre but nothing seems to happen

remove the cap, pull the rubber bit out, tap out the green bit, then switch it round, but this is where your problems start, as it does not seem to pump the tyer up.

Change the internal parts of the head to adapt to the valve type you're using.

http://www.bikenewyork.org/resources/nuts_bolts/tires.html

See solution 2

i have just bought a mini g masterblaster but when i try and pump my tyre up, nothing happens.

Is the chuck configured for the type of valve stem you're using and the thumb lock activated?