Answer

Hopefully the starch you have is alright – I think it might just need dissolving differently.
 The best way to make starch powder into solution is to add a little cold water to the starch and mix into a paste. Add boiling water to the paste, stirring all the time. The solution should turn clear, although if it is still not clear, boil briefly until it does turn clear. Allow to cool before use. This does not store for very long, so is best made up fresh.
 Usually a 1% solution is made. Add a little cold water to 1g starch powder & mix into a paste. Make up to 100ml with boiling water, stirring all the time.