What is ProtonCash? 
I can't find any BCH wallet called ProtonCash. Do you mean "ElectronCash": https://electroncash.org/
If yes, and it's asking for a "master key" instead of a list of private keys, then you have selected the wrong option when creating the wallet... Start creating a new wallet using "File -> New\Restore". After selecting a name for your wallet, you need to select "Import Bitcoin Addresses or Private keys":
DO NOT select "Standard wallet"!
You will then be prompted to enter a list of Address or Private keys:
Enter your private keys (one per line) and then click Next. The wallet will be created and you should be able to see your BCH balance.
I can't find any BCH wallet called ProtonCash. Do you mean "ElectronCash": https://electroncash.org/If yes, and it's asking for a "master key" instead of a list of private keys, then you have selected the wrong option when creating the wallet... Start creating a new wallet using "File -> New\Restore". After selecting a name for your wallet, you need to select "Import Bitcoin Addresses or Private keys":
DO NOT select "Standard wallet"!
You will then be prompted to enter a list of Address or Private keys:
Enter your private keys (one per line) and then click Next. The wallet will be created and you should be able to see your BCH balance.