"No rule to make target" on make

Hi,
i'm new here and also just take my first steps with Nginx-Module-Programming.

Last week I've create my first Test following this:
https://blog.csdn.net/xiangguiwang/article/details/70174908

and all works.
Today i've changed the cpp-File a little bit and tried again.
The Configuration runs without a Problem, but when i use "make" it says:

make[1]: *** No rule to make target '/home/user1/test//ngx_http_hello_world_module.cpp', needed by 'objs/addon/test/ngx_http_hello_world_module.o'. Stop.

Then i delete all and create the first (hello_world from the site above) again, but also with the same result.
The module-Cpp is an exact copy of the hello_world and the config contains the following:

ngx_addon_name=ngx_http_hello_world_module
HTTP_MODULES="$HTTP_MODULES ngx_http_hello_world_module"
NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_hello_world_module.cpp"

Can anyone tell me, what's going on now?