Why does it say TFM File not found Even Though It is Installed?

I’m an amateur when it comes to LaTeX, so please bear with me. I am trying to use a package, but this error persists:

Font OMX/ksd/m/n/10=ksd10 at 10.0pt not loadable: Metric (TFM) file or installed font not found.

Now I’ve seen a number of responses to this question, but nothing worked with me (or perhaps I couldn’t understand them?).

Just in case, here is the document:

documentclass[a4paper, 12pt]{article}


usepackage{fontspec}
usepackage{polyglossia}
usepackage[kashidasymbol]{curext}
usepackage{ramzarab}
usepackage{rydarab}
input amarabiwords
funwithdots


setmainlanguage{arabic}
setotherlanguage{english}
setmainfont[Script=Arabic]{Amiri}
newfontfamilyenglishfont[BoldFont={LMRoman12-Bold}, ItalicFont={LMRoman12-Italic}]{LMRoman17-Regular}
newfontfamilydhahabi[Script=Arabic]{Aldhabi}

begin{document}
{
arabmath
$${csum_{b=T-1}^{s}} c{{}^b}$$
}
end{document}

You could ignore the preamble. The package I’m struggling with is curext. I have the TFM file in the system, but it seems like it could never been found. Any help?