Do you mean a compiler supporting Fortran 2018, or version 18.0 of the compiler? If the former, see The Easy and Fast Way to Install JUST Fortran with Intel® oneAPI - Intel Communities. If the latter, you would need to have a paid support contract get it from the Intel Registration Center, though I would question why you think you need that.
No, that would not be a reason. What is the problem symptom? If there's an error message, please show a screenshot. If the error is that there are missing DLLs, then you should just need to install the run-time redistributables. Go to Intel® oneAPI standalone component installation files . In the left column, select "Runtime Versions" and select your OS.