The error message is kinda explicit: "initializer is not a constant" - which it isn't.
The address of an object is not a constant value as far as the compiler is concerned, because it is defined by the linker which locates the program and its data inside the memory space. The compiler doesn't - if defines everything in terms of it's size, and lets the linker sort out the actual address.
But you can't use the value of any variable as a constant value under any circumstances - which is what you are trying to do.
Even if you did this:
int ii = 6;
static const tMax teststr = {
ii,
0,
0};
You would get the same error!