Qt and third-party dlls, the essence of the error is: file not recognized: File format not recognized and how to fix it?

Question

Qt

Good afternoon!
Development underway: Qt 5.7.0 + MinGW 5.3.0 (32-bit) + Qt Creator 4.0.2, Win7.
I was interested in the essence of the "file not recognized: File format not recognized" error and how to deal with it if there are no library sources.
I encountered such an error when connecting wsp32.dll [1] - an implementation of the wake protocol for working with the device via rs232.
PS In a particular case, the library sources are available, and with some changes I will eventually drag them into the project as separate .cpp + .h, but I would like to understand the causes of the error and alternative ways to fix it.
1. wsp32.dll and its sources in a zip archive
2. zip archive with a test Qt project that connects this library

Answer 1

How exactly did you connect the dll?
You can’t just take it and add it to the project, usually a lib is attached to it for connection. Or you can connect dynamically.