The environment variables set by copSSH are not the same than the one found in a git bash Windows. (see also OpenSSH on Windows)
You may need to redefine the $HOME variable to the one used by copSSH. See this thread for additional example of HOME redefinition.
By default, HOME=/c/Users/Nick.
Try:
export HOME=/c/copSSH/home/Nick To make it permanent (each time you open a bash shell), you can try adding this line to your .bashrc under c:\Users\Nick (c:\Users\Nick\.bashrc)